Sharepoint pages cannot be async, just Web Parts
http://daniellarson.spaces.live.com/blog/cns!D3543C5837291E93!180.entry
Only AJAX/jQuery can be used
http://www.codefornuts.com/2009/09/forcing-sharepoint-into-asynchronous.html
http://jpoint.codeplex.com/
(via http://blogs.msdn.com/sharepoint/archive/2007/11/29/preview-into-wss-3-0-sp1-and-sharepoint-server-2007-sp1.aspx)
KB for the Sharepoint 2007 AJAX support
http://support.microsoft.com/kb/941955
Silverlight Webpart for Sharepoint 2007
http://www.liveside.net/blogs/developer/archive/2007/12/05/add-silverlight-to-sharepoint-2007.aspx
http://blogs.msdn.com/davbosch/archive/2007/02/24/smartpart-for-sharepoint-now-with-ajax-support.aspx
Get the Sharepoint 2007 AJAX toolkit from CodePlex http://www.codeplex.com/sharepointajax
Other Sharepoint AJAX posts:
http://blogs.msdn.com/italy/archive/2009/05/16/ajax-control-toolkit-nuova-versione-disponibile.aspx
SharePoint 2007 and AJAX Using ASP.NET for AJAX in SharePoint Siteshttp://weblogs.asp.net/wkriebel/archive/2005/12/27/SharePointAJAXFeedbackSample.aspxhttp://weblog.vb-tech.com/nick/archive/2006/01/03/1398.aspxhttp://www.sharepointblogs.com/remcoploeg/archive/2006/01/27/4854.aspxhttp://www.andrewconnell.com/blog/archive/2005/07/10/1713.aspxhttp://msmvps.com/blogs/anguslogan/archive/2005/07/09/56884.aspxhttp://blogs.tamtam.nl/mart/AJAXSeamenMassiveMultiplayerBattleships.aspxhttp://blogs.flexnetconsult.co.uk/colinbyrne/PermaLink,guid,932884be-2276-4236-8df4-f360149b5fd1.aspxAJAX + MOSS 2007 http://blog.thekid.me.uk/archive/2007/01/19/using-asp-net-ajax-with-sharepoint-moss-2007.aspxhttp://msmvps.com/blogs/anguslogan/archive/2005/07/09/56884.aspxSharepoint AJAX Toolkit http://www.capdes.com/2007/02/microsoft_office_sharepoint_se.htmlhttp://sharepoint.microsoft.com/blogs/mike/Lists/Posts/Post.aspx?ID=3http://weblogs.asp.net/scottgu/archive/2007/02/20/asp-net-ajax-and-sharepoint.aspxhttp://blogs.msdn.com/acoat/archive/2007/02/23/sharepoint-and-asp-net-ajax.aspxSharepoint + AJAx on Exchangehttp://www.sharepointblogs.com/remcoploeg/archive/2006/01/27/4854.aspxSharepoint + AJAx as a Feedback Form(via http://blogs.officezealot.com/rbedell/archive/2005/12/28/8891.aspx )http://weblogs.asp.net/wkriebel/archive/2005/12/27/SharePointAJAXFeedbackSample.aspx