Microsoft ASP.NET AJAX 1.0 Beta 2

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.
Download: Microsoft ASP.NET AJAX 1.0 Beta 2