free, original DHTML & Javascripts to enhance your web site...
http://dynamicdrive.com/

"Ext is a client-side, 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." In the fall of 2006, Jack released version .33 of yui-ext, which turned out to be the final version of the code under that name (and under the open source BSD license). 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 layout:'fit',framework. A company was formed in early 2007, and Ext is now dual-licensed under the LGPL and a commercial license. The library officially hit version 1.0 on April 1, 2007"
http://extjs.com/

The Json.NET library makes working with JSON formatted data in .NET simple.
Quickly read and write JSON using the JsonReader and JsonWriter or serialize your .NET objects with a single method call using the JsonSerializer
http://www.codeplex.com/Json