Backbone.js gives structure to web applications by providing models with key-value binding and custom events, collections with a rich API of enumerable functions, views with declarative event handling, and connects it all to your existing API over a RESTful JSON interface.
The project is hosted on GitHub, and the annotated source code is available, as well as an online test suite, an example application, a list of tutorials and a long list of real-world projects that use Backbone.
You can report bugs and discuss features on the GitHub issues page, on Freenode IRC in the #documentcloud channel, post questions to the Google Group, add pages to the a wiki or send tweets to @documentcloud.
Backbone is an open-source component of DocumentCloud.
Via Leon Zhang