Ext JS a Javascript Framework with Ajax and Stunning UI

Ext is a JavaScript framework for building web applications. In early 2006, Jack Slocum began working on a set of extension utilities for the Yahoo! User Interface (YUI) library. These extensions were quickly organized into an independent library of code and distributed under the name “yui-ext“. By the end of the year, the library had gained so much in popularity that the name was changed simply to Ext, a reflection of its maturity and independence as a framework.

Requirements: Internet Explorer 6+, FireFox 1.5+, Safari 2+, Opera 9+
Demo: http://extjs.com/deploy/ext/docs/index.html
License: LGPL License