Announcing the new ASP.NET Ajax V1 Beta available for download from http://ajax.asp.net/Default.aspx?tabid=47 
I have been looking forward to this… This will be one major step for WEB 2.0, more and more sites will begin to use it. Hopefully future version of WSS have this included 🙂

With ASP.NET AJAX, developers can quickly create pages with rich, responsive UI and more efficient client-server communication by simply adding a few server controls to their pages. This new Web development technology from Microsoft integrates cross-browser client script libraries with the ASP.NET 2.0 development framework. ASP.NET AJAX provides developers building client-based Web experiences with a familiar development process and programming model that they already know from using server-side ASP.NET development. Because ASP.NET AJAX is integrated with ASP.NET, developers have full access to the built-in ASP.NET 2.0 application services and the entire .NET Framework.

Download it from HERE