The .Net based answer of Microsoft to AJAX, ASP.NET AJAX and formerly known as Atlas has been released officially. It includes both client SIDE and server side APIs. It provides developers the ease for creating AJAX style web applications through seamless integration with .NET Framework and Microsoft platform.

The official version incorporates all the features which were included in the beta version. Some of the changes from the time Release Candidate was released are substitution caching support, performance enhancements and a number of other bug fixes. Besides the APIs, the company is also releasing the client side source code for ASP.NET AJAX under the Microsoft Permissive License and the server side source code under the Microsoft Reference License. In the future Orcas, code name for Visual Studio will directly incorporate ASP.NET AJAX.

This is what the website of Microsoft says about ASP.NET AJAX

With ASP.NET AJAX, you can:

• Create next-generation interfaces with reusable AJAX components.
• Enhance existing Web pages using powerful AJAX controls with support for all modern browsers.
• Continue using Visual Studio 2005 to take your ASP.NET 2.0 sites to the next level.
• Access remote services and data directly from the browser without writing a ton of complicated script.
• Enjoy the benefits of a free framework with 24x7 technical support provided by Microsoft.

It's free and now available officially to improve your web experiences. Click here to download.