Alloy UI is a JavaScript UI library, a CSS framework, a set of HTML recipes and a taglib library, all combined to empower developers across multi-skilled teams deliver rich and dynamic applications.
It is built by the developers of Liferay, has a lot of ready-to-use components & requires Yahoo! User Interface Library to run.
The components include:
  • auto-complete
  • charts
  • color picker
  • calendar
  • tooltips
  • forms
  • treeview
  • image gallery
  • & much more..
The framework comes with full set of demos & not documented yet (currently in a preview release).

Requirements: YUI
Compatibility: All Major Browsers
Website: http://www.alloyui.com/
Demo: http://www.alloyui.com/demos.php
Download: http://www.alloyui.com/download.php