I found these cool links while trying to find about AJAX. For some unknown reason my custom AJAX based webparts are not working on SharePoint 2007 sites. I was looking for fix so find these links
http://daniellarson.spaces.live.com/blog/cns!D3543C5837291E93!934.entry?wa=wsignin1.0
http://www.virtual-generations.com/2007/02/22/smartpart-for-sharepoint-aspnet-ajax-support/
http://blogs.claritycon.com/blogs/george_durzi/default.aspx
http://weblogs.asp.net/jan/archive/2007/02/26/using-the-ajax-control-toolkit-in-sharepoint.aspx
http://www.capdes.com/2007/02/microsoft_office_sharepoint_se.html
http://sharepoint.microsoft.com/blogs/mike/Lists/Posts/Post.aspx?ID=3
http://support.microsoft.com/kb/941955
Updated Articles on ASP.NET AJAX with SharePoint – Updated SDK
ASP.NET AJAX in Windows SharePoint Services
Overview: ASP.NET AJAX and Web Parts in Windows SharePoint Services 3.0
Installing ASP.NET AJAX Extensions in Windows SharePoint Services
Walkthrough: Creating a Basic ASP.NET AJAX-enabled Web Part
