Scott announced today the future of our Ajax product plans. The stuff that has been code named "Atlas" in the previous CTPs is now solidifying into a real product with a real standard Microsoft name. In particular the "Microsoft AJAX Library" (client side script library) and "ASP.NET 2.0 AJAX Extensions" (the stuff that makes it easy to write ajax code w/ ASP.NET). In addition there will be an ASP.NET AJAX Control Toolkit which will provide some shared source controls and that you can use w/ ASP.NET.
If you have been intrigued w/ AJAX, this is some great news to get some actually supported libraries and controls fairly soon that can give you that great AJAX Web experience.