Daniel Larson’s ASP.NET AJAX Extensions Toolkit for SharePoint.
Get the code from the Source Code link.
Note: This project DOES NOT provide any support for working with the “Ajax Control Toolkit”.
This is a base framework built on top of the Microsoft AJAX Library and ASP.NET AJAX for deploying client-side AJAX Web Parts and controls that work against web services and Xml feeds utilizing the ASP.NET AJAX framework.
Project dependencies: ASP.NET Ajax RTM. Get it at http://ajax.asp.net.