JQuery is an open source, fast, easy to use, Javascript library. jQuery is a must have library for client side developers. What were once cumbersome Javascript tasks that took many lines of code, can now be done quickly, efficiently, with very little code. It handles DOM manipulation, CSS, Ajax, events and animation. jQuery is tested against all major browsers and is CSS compliant. For Visual Studio developers, Microsoft has announced inclusionof jQuery in Visual Studio 2010. For intellisense in your Visual Studio 2008 projects you can download the intellisense file (vsdoc.js) from 
De JQuery site:
En voor een rechtstreekse link naar documentatie (incl. zoekfunctie):
jQueryUI is an open source library of client side components based on jQuery. jQuery UI provides components like accordion, tabs, drag and drop and many others. One of the most exiting tools jQuery UI offers is an online GUI called Theme Builder. With the theme Builder, you can select from an existing collection of pre-defined themes or create your own theme. jQuery UI will generate the css styles and icons for you. Go to:  
Zie verder: artikel Using jQuery UI in DotNetNuke modules (SDN Magazine, mei 2009)