ASP .NET Ajax Introduction:
ASP .NET Ajax Job Support
The ASP.NET AJAX Control Toolkit is a open source project that contains the number of AJAX-enabled controls & extenders. If you intend to use these controls, then you need to download the runtime binaries to your local computer & add an reference to your Visual Studio 2005 or 2008 project.
To use ASP.NET AJAX you need to download & then install the free framework to your local computer. This will add new project templates for creating the AJAX-enabled Web sites & new tools in the Toolbox area of the Visual Studio 2008.