Microsoft ASP.NET AJAX official page: www.asp.net/ajax
ASP.NET AJAX Control Toolkit: www.asp.net/ajax/ajaxcontroltoolkit
ASP.NET AJAX Control Toolkit Samples: www.asp.net/ajax/ajaxcontroltoolkit/samples
ASP.NET AJAX Documentation: www.asp.net/AJAX/Documentation
ASP.NET AJAX Forums: http://forums.asp.net/default.aspx?GroupID=34
MIX Videos: http://sessions.visitmix.com