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.
AngularJS lets you write client-side web applications as if you had a smarter browser. It lets use good old HTML (or HAML, Jade and friends!) as your template language and lets you extend HTML’s syntax to express your application’s components clearly and succinctly.
Cappuccino is an open source application framework for developing applications that look and feel like the desktop software users are familiar with.
The core includes a simple API for defining applications which are made up primarily of routes and events. By driving application development around a small and specific API, Sammy attempts to keep your code organized while still allowing a lot of breathing room to define your own style and structure.