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

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