Telerik RadControls for ASP.NET AJAX is the next generation of Telerik ASP.NET suite. It is built on top of ASP.NET AJAX and provides a new set of capabilities. It is a prerequisite to have ASP.NET AJAX installed when using Telerik RadControls for ASP.NET AJAX. This section provides a list of resources which will help you get started with generic ASP.NET AJAX.
http://msdn.microsoft.com/en-us/library/bb398874.aspx
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=ca9d90fa-e8c9-42e3-aa19-08e2c027f5d6
http://msdn.microsoft.com/en-us/library/ff647506.aspx
http://www.asp.net/ajaxlibrary/Browser%20Security%20Settings%20for%20Ajax%20Enabled%20ASPNET%20Pages.ashx
http://msdn.microsoft.com/en-us/library/ee341002.aspx
http://msdn.microsoft.com/en-us/library/bb398863.aspx
http://www.asp.net/ajax/videos
http://www.asp.net/ajax/ajaxcontroltoolkit/samples/
http://www.asp.net/ajax/videos#AJAX%20Control%20Toolkit%20Videos
http://forums.asp.net/1022.aspx?ASP.NET+AJAX+%2b+Ajax+Control+Toolkit