I've heared from many people talking about AJAX support in ASP.NET so here is the news from its sources ( Miscrosoft's developers of the project ), The project is called Atlas

We are now well into the final RTM milestone of the ASP.NET 2.0 and Visual Web Developer 2005 release. Having reached our ZBB (Zero Bug Bounce), we are now locked down on our feature set, and we’re focusing on the final quality, performance, and reliability push.

At the same time, we have started to work on our next release. One area we’ve been looking at for a while is the growing popularity of richer user experiences in browsers, through AJAX (Asynchronous Javascript and XML)-style programming.

The popularity of AJAX shows the growing demand for richer user experiences over the web. However, developing and debugging AJAX-style web applications is a very difficult task today. To write a rich web UI, you have to know a great deal of DHTML and JavaScript, and have a strong understanding of all the differences and design details of various browsers. There are very few tools to help your design or build these applications easily. Finally, debugging and testing these applications can be very tricky.

Source ScottGu's Blog