More About Bootstrap :

Twitter Bootstrap is a front-end toolkit for rapidly developing web applications and is  built with Less, a flexible pre-processor offering more power than  traditional CSS (variables, nested declarations, mix-ins, operations,  and color functions)
Twitter Bootstrap is a free collection of  tools for creating websites and web applications. It contains HTML and  CSS-based design templates for typography, forms, buttons, charts,  navigation and other interface components, as well as optional  JavaScript extensions.
It is the most popular project in GitHub and is used by NASA and MSNBC among others.
Origin
 Bootstrap was developed by Mark Otto and Jacob Thornton at Twitter as a  framework to encourage consistency across internal tools. Before  Bootstrap, various libraries were used for interface development, which  led to inconsistencies and a high maintenance burden. According to  Twitter developer Mark Otto, in face of those challenges (source wikipedia)
Features 
Twitter Bootstrap consist a lot of useful resources for template.
jQuery  plugins, Complete styleguide documentation, HTML components, 12-column  grid system, LESS file, Responsive Features according to resolutions and  devices.

Here, I have collected list of best free and paid  awesome Twitter Bootstrap Themes and Templates also Twitter Bootstrap 3 Themes and Templates.

1) Free Bootstrap Themes And Templates From Bootstrappage : (Demo| More Info | Free Download)

Bootstrappage provide free quality bootstrap based themes and templates.

2) Bootbusiness  Free Bootstrap Theme : (Demo |More Info | Free Download )

Bootbusiness  mainly focused for business and corporate websites. This can be used to  list and market various products of your businesss.Designed in HTML5  and CSS3 techniques.

3) United- Free Bootstrap Template: (Demo | More Info | Free Download )

United is free Bootstrap theme provided free by Bootswatch.

4) Bootstrap Live WYSIWYG HTML5 Editor: (Demo| More Info | Download)

Bootstrap Live Editor is a WYSIWYG HTML5 Editor built for Bootstrap. It offers a nice and elegant way to edit and beautifyhtml content with Bootstrap ready UI elements.

5)Virgin Admin Bootstrap Template : (Demo |More Info | Download)

It's  not a theme, it's an app. Contains the latest and best in market  technologies. Virgin is built as an all purpose theme with widgets,  admin dashboards, portfolios, galleries and everything included.

6) Output Responsive Multi-Purpose Wordpress Bootstrap  Theme : (Demo | More Info |Download)

Output  is the result of more then two years experience of improving usability  of our themes. This multipurpose theme with a wide set of functionality  will suit any needs and tasks you want to accomplish. See for yourself,  this theme comes with a powerful GT3 Page Builder that has already won the respect among our customers. It’s Wocommerce Ready which means you can deploy a shop in a matter of seconds. If you are a foreign customer or want to trade abroad, no problem WPML MULTI LANGUAGE plugin is already integrated, so you can translate your theme to your language  right away, no additional plugins required. At last for those of you  who requires flexible a customizable contact forms we added Contact Form 7 support. So now you can easily add and customize any kind of forms. And  all this tangible benefits are wrapped around clean and elegant design  that can be easily customized. Output is one of those low hanging fruits  that you can’t pass by without having it.

7)Bootstrap Extra Pages Layouts Responsive Website Template : (Demo | More Info |Download)

Bootstrap Extra Pages Layouts Responsive Website Template is bootstrap ready responsive web template.

8) Pixel - Responsive Bootstrap HTML5 Template : (Demo | More Info | Download)

Pixel  is a agency and corporate theme. Its simple and clean HTML5 & CSS3  Template. Its a full responsive theme built with Bootstrap.

9) SimpliQ Flat & Responsive Admin Bootstrap Template: (Demo | More Info | Download)

SimpliQ Flat & Responsive Admin Template is a fully featured, premium, Bootstrap Admin Template with Modern Flat Style.
Built with LESS, delivered with LESS and CSS Files.
If  you looking for dashboard template for your application SimpliQ Flat  & Responsive Admin Template is perfect solution for you. SimpliQ  Flat & Responsive Admin Template contains many plugins and widgets  ex. charts, chats, weekly Stats, last users, To-Do list, support tickets  and many more, so your app will be look awesome.
SimpliQ Flat & Responsive Admin Template based on Bootstrap 2.3.2 from Twitter. It works on all major browsers and optimizes itself for tablets and mobile phones.
SimpliQ Flat & Responsive Admin Template support Retina Displays, all elements look amazing!
SimpliQ Flat & Responsive Admin Template contains over 500 high resolution icons.

10)Start Up Admin Bootstrap Theme : (Demo |More Info |Download)

Start Up - Responsive Admin template was built with the popular Bootstrap framework from Twitter and powered with Sass. Start Up Admin template comes with customized variables that make this admin template very unique.
The  admin template adapts seamlessly with any device such as desktop, mac,  tablets and mobile phones. You can use this template if you are building  an administrator panel for any website.

11) Chromatron HTML5 Admin Backend : (Demo| More Info | Download )

Chromatron  is a simple and professional HTML5 template for your backend  administration or user interface, both for desktop and mobile. Built on  latest Twitter
Bootstrap and powered with LESS,  Chromatron will save you hours in developing your project. Template is  available in 4 default colors and packed with basic and popular user
interface elements and widgets.
Built on Twitter Bootstrap
Bootstrap  is one of the most complete front-end toolkits over the internet. Thats  why we decided to use it as our skeleton framework for all upcoming  templates. Maintaining native Bootstrap functionality, enriched of  pleasing design and tons of new template features, makes it very  powerful UI kit for rapid development.

12) Mafioso HTML 5 Responsive Bootstrap Template : (Demo | More Info | Download)

Mafioso   is fully responsive bootstrap template with 8 HTML pages,8 psd  files,sortable portfolio,lightbox2 image gallery,2 pricing tables etc..

13) Proper - Responsive Real Estate Template : (Demo | More Info | Download)

Proper  is a simple, easily customized Responsive HTML template that can be  used to build a real estate site with listings and property details  pages

14) Bootstrap Responsive Website Template : (Demo | More Info | Download)

This Bootstrap template is suitable for fashion and modeling related sites but you can configure for your business too.

15) Anubis - Responsive Bootstrap WordPress Theme : (Demo |More Info|Download )

Anubis  is an ultra responsive, beautiful WordPress theme that is perfect for  freelancers, agencies, designers and creative people. It is an elegant  & modern solution packed up with an incredibly great amount of high  quality features.
Responsive Design and Retina Ready – Serve an optimised version of the volumes theme to your visitors  using tablet and mobile devices. It is optimized for Retina Displays  (used in iPhone, iPad, iPod Touch and MacBook Pro Retina).
Post formats – Support for post formats means you can fill your blog with your  self-hosted video, audio, images, galleries and of course good old  standard posts.

16) Nyirok - Responsive Portfolio & Business Bootstrap JoomlaTemplates : (Demo | More Info| Download)

Nyirok  is a stunning, clean and fresh Joomla templates. This templates easily  fits for any kind of website demographics. Aside from just looking  beautifully polished and clean, it comes packed with features and  options, powerful T3 Joomlart Framework,a slideshow module, easily  configured various modules positions, a newsletter plugin, and a lot  other best and selected extensions . Nyirok is a responsive templates and optimized for tablet and any others mobile screen. So, If  you’re looking for a fresh new Joomla templates, than look no further.

17) Grid - Responsive Portfolio Retina Template : (Demo | More Info | Download)

If you love flat and retina-supported design, GRID will surely amaze you at the first sight. It is the fully responsive  HTML5 & CSS3 template that best used for blogging, personal  portfolio, even business portal. The template layout and mechanism are  enhanced to deliver all images and graphics with WOW effect.
GRID works seamlessly on a wide range of devices including PCs, mobiles,  laptops, etc. It has the sophisticated layout with colorful design and  carefully crafted graphic (that is retina supported) helping you to  attract more visitors to your website.

18) Jarvis - Smart Admin Template : (Demo | More Info | Download)

Simple yet innovative, JARVIS admin template is one of a kind. Jarvis utilizes LESS (also includes commented CSS) and uses state of the art custom cut features that are tested for  reliability and robust performance with a blend of the latest design  trends. Jarvis is constantly evolving, it is updated regularly and new  features are added from time to time.

19) Minx - Responsive HTML5 Template : (Demo |More Info | Download)

Minx is a professional responsive creative HTML5 portfolio template which has been built using the Twitter Bootstrap framework. 
The  template comes complete with 28+ pages, six colour schemes in both  light and dark styles. Sliders, carousels, PrettyPhoto, Pinterest  photostream, a working contact form and also uses lots of features which  are available as part of Twitter Bootstrap.

20)Metronic - Responsive Admin Dashboard Template : (Demo | More Info | Download)

Metronic is a responsive admin dashboard template powered with Twitter Bootstrap Framework for admin and backend applications. Metronic has a clean and intuitive metro style design which makes your next project look awesome and yet user friendly.  Metronic comes with a huge collection of plugins and UI components and  it works in all major web browsers, tablets and phones.

21) Neuron Responsive WordPress Theme : (Demo| More Info | Download)

Neuron  Responsive WordPress Theme is a clean and modern theme design with 3  built in theme colors to suit your needs. With its high contrast design,  Neuron will give your next project the eye catching edge to stand out  from the crowd, and it’s intuitive interface will ensure the user  experience you’d expect from a premium WordPress theme. Built on  Bootstrap, Neuron has been carefully crafted to be easily customized and  flexible enough utilizing custom built plugins. Also included in the  package is the popular LayerSlider plugin which has several Parallax and  3D slider effects which can be fully customized via the WordPress admin  panel. Being responsive the theme layout is fluid and is compatible  with all mobile and tablet devices.

22)Lava - Single & Multi Page BootstrapTheme: (Demo | More Info | Download)

Lava  is a beautiful, unique Bootstrap theme built for the creative business  or individual. Its powered by HTML5 and the latest CSS3 technologies.  Designed for multipurpose use, this theme includes over 10 HTML pages,  CSS3 animations, pricing charts, a working contact form, sign up pages,  and lots of other features.

23) Serenity Minimal One Page Bootstrap Template : (Demo | More Info | Download)

Serenity is a minimal bootstrap template. Available in 2 layouts ( Wide &  Narrow ). Crafted with keeping in mind the softness & clarity of  feathers. This template is for everyone who loves minimal designs.

24) Fitnex - Responsive HTML Landing Page : (Demo | More Info | Download)

Fitnex is a Multipurpose Landing Page Based on Bootstrap Framework , it include 3 colors/skins . 
This Template is the perfect showcase for your Company or Service.

25) Peach Realestate - Wordpress Bootstrap Theme: (Demo | More Info | Download)

Peach  Realestate - Wordpress is an impressionistic, responsive Bootstrap  theme.his CMS site is built to work across a wide range of medium  including all major mobile browsers with ease and comfort of the user.  With the combination of the automatic Google Map Plotter, LocalStorage  based shortlist widget and responsive sliders, gallery and videos makes  this a very unique theme.

Update :

Bootstrap has released its latest version Bootstrap 3. In  this version new flat design, optional theme,mobile-first  approach,always responsive,New powerful grid system,four tiers of grid  classes,New Glyphicons icon font,JavaScript plugins are rewritten,two  new components (list group,panel),Improved components,Smallest file size  etc.. are included.
I have collected some of awesome themes and templates based on Bootstrap 3. This list includes WordPress ,admin, one page, landing page, web app, mobile app, eCommerce,HTML5 and other themes and Templates :

1) Ace - Responsive Bootstrap 3 Admin Template : (Demo |Download )

2) Mars - Responsive Admin Bootstrap 3 Template : (Demo |Download )

3) Clean Canvas - Bootstrap 3 Business Theme : ( Demo |Download )

4) Aveta - Responsive Bootstrap 3 Template: ( Demo |Download )

5) SimpliQ Flat & Responsive Admin Bootstrap 3Template : (Demo | Download )

6) Lovinflat - One Page Bootstrap 3 Theme : ( Demo |Download )

7) Unicorn - Bootstrap 3 Admin Template : ( Demo |Download )

8) Ortax - Bootstrap3 HTML5  Multipurpose Template : ( Demo| Download )

9) Light Blue - Responsive Bootstrap 3 Admin Template : (Demo| Download )

10) Nicole Fashion Bootstrap 3 eCommerce Template : ( Demo |Download )

11) 3 in 1 - Admin + Front End + E-Commerce Multipurpose Bootstrap 3 Template: ( Demo | Download)

12) Pheel - Responsive MultiPurpose Bootstrap 3 Theme : (Demo | Download )

13) Detail Admin - Responsive Bootstrap 3 Theme : ( Demo |Download )

14) Horizonal Unique Creative OnePage Bootstrap 3 HTML5 Template : ( Demo | Download )

15 ) Base Bootstrap 3 Admin Template : ( Demo | Download )

16 ) Syndicate - All Purpose Bootstrap Retina Bootstrap 3 Template ( Demo | Download )

17) Earth - Responsive HTML Bootstrap 3 Template : ( Demo |Download )

18) Smooth Sailing - One-Page Bootstrap 3 Landing Page: (Demo | Download )

19) Metro Bootstrap 3 Admin Theme : ( Demo | Download )

20) todo - Web Application and Admin Panel Bootstrap 3  Template : ( Demo | Download ) 

21) Flatty - Flat Bootstrap 3 Administration Template : ( Demo |Download )

22) Alpona - A Clean Responsive Flat Bootstrap3 Admin Template : ( Demo | Download )

23) The Story - Flat Bootstrap Business Template : ( Demo |Download )

24 ) ColorCloud - One-Page Design, 3-Layer Parallax Bootstrap 3  Theme : ( Demo | Download )

25) OlsonKart - Bootstrap 3 E-Commerce Theme : (Demo | Download )

26) Melon – Flat & Responsive Bootstrap 3 Admin Template : (Demo | Download )

27) Cotton - Responsive Bootstrap 3 Single Page Template : (Demo | Download )

28) Jugoos - One page Creative Bootstrap 3 Template : ( Demo |Download )

29) Aventador - One Page Bootstrap 3 Theme : ( Demo |Download )

30) first - Mobile First Web App Bootstrap 3  Theme : ( Demo |Download )

31) Diamond - Bootstrap 3 Landing Page Template : ( Demo | Download )

32) FLATY - Premium Responsive Bootstrap 3 Admin Template : ( Demo | Download )

33) OlsonAdmin - Basic Bootstrap 3 Admin Theme : ( Demo |Download )

34) Interion - Responsive One Page Bootstrap 3 HTML Template :  ( Demo | Download )

35 ) Bootstrap 3 Responsive Pricing Tables : ( Demo |Download )

36 ) Visionmax - Bootstrap 3 Html 5  Multipurpose Template : (Demo | Download )

37) Cosos - Bootstrap 3 Coming Soon Template : ( Demo |Download )

38) Onefrog Clean Bootstrap 3 Theme : ( Demo | Download )

39) Slim - Responsive & Minimal Bootstrap 3 Coming Soon Page : ( Demo | Download )

40) Awesome Admin Bootstrap 3 Template : ( Demo |Download )

41) News Grid - WordPress Bootstrap 3 Magazine Theme: (Demo | Download )

42) ACME - Responsive Bootstrap 3 Admin Template : ( Demo |Download )

43) Gravida - Responsive & Modern Bootstrap 3 HTML5 Template : ( Demo | Download )

44) Casper - One Page Complete Bootstrap 3 Template : ( Demo| Download )

45) Salad - Responsive Bootstrap 3 Coming Soon Page Template : (Demo | Download )

46 ) Ambrosia - Web Application Bootstrap 3 Theme : ( Demo |Download )

47) GYM - Sport Retina Responsive Bootstrap 3 Template : (Demo | Download )

48) SLICK - One Page Bootstrap 3 Theme : ( Demo |Download )

49) Se7en - Web & Mobile Application Bootstrap 3  Template : (Demo | Download )

50) Flat & Scroll 2 - Bootstrap 3 One Page Theme : ( Demo |Download )

51) RainDrop - Clean Bootstrap 3 eCommerce PrestaShop Theme: ( Demo | Download )

52) Shopfrog - Modern E-Commerce Bootstrap 3 Template : (Demo | Download )

53) SimpleApp - Single Bootstrap 3 Page Scrolling Site Template : (Demo | Download )

54) Fasi - Responsive Bootstrap 3 Mobile App Theme : ( Demo | Download )

55) Sunshine - Responsive Bootstrap 3 Hotel Template : ( Demo| Download )

56) StrapPress - WordPress Bootstrap 3 Theme : ( Dem0 |Download )

57) Mochito - Responsive Onepage Bootstrap Portfolio Template : (Demo | Download )

58) DOT - Bootstrap 3 One Page Template : ( Demo |Download )

59) Bistro Store Bootstrap 3  e-Commerce WordPress Theme : (Demo | Download )

60) Colorfrog Corporate Business Bootstrap 3 Theme : ( Demo |Download )

61) Room Cartoons Photography Bootstrap 3 WordPress Theme : ( Demo | Download)

62) Responsive Professional Portfolio Bootstrap 3 Theme : (Demo | Download )

63) Verde - Bootstrap 3 Minimal Coming Soon Template : ( Demo| Download )

64) Digital - Bootstrap 3 Coming Soon Template : ( Demo |Download )

65) Norris - Elegant Retina-ready Bootstrap 3 Onepage Template : ( Demo | Download )

66) Cassius - Modern & Flat Bootstrap 3 Multipurpose Template : (Demo | Download )

67) Orchestra - Bootstrap 3 Responsive Symphony CMS Theme : (Demo | Download )

68 ) Great Shop Responsive Bootstrap 3 Magento Theme : (Demo | Download )