November 2005
ASP.NET 2.0 Released along with Visual Studio 2005 (No ASP.NET AJAX)
January 2007
ASP.NET AJAX v1.0 released as an add-on to ASP.NET 2.0 (Works with Visual Studio 2005)
May 2007
ASP.NET "Futures" a developer preview of some of the features considered for future releases released as a CTP
July 2007
ASP.NET "Futures" CTP Updated
November 2007
ASP.NET 3.5 and Visual Studio 2008 released (ASP.NET 3.5 contains built-in newer version of ASP.NET AJAX, ListView, DataPager and LinqDataSource controls)
December 2007
ASP.NET 3.5 Exensions (CTP Version containing new features for ASP.NET, AJAX and Silverlight)
Going further, ASP.NET "Futures" would still be updated as CTPs offering a developer preview of further new things considered for future versions, at an early stage. However, the Dynamic Data Controls that were a part of the ASP.NET "Futures" (July 2007 CTP) are becoming obsolete and the ASP.NET 3.5 Extensions Dynamic Data Controls is what would be continued and shipped.
If you have attended my sessions on ASP.NET "Futures" and Dynamic Data Websites, you would be excited to hear that with this extensions CTP, you get much more better support for customization, validation etc.,
Currently I am playing with the same and would follow this post up with newer posts on the same.
Cheers !!!