What is Atlas?

Atlas is a free framework for creating AJAX applications with Microsoft’s ASP.NET 2.0. Using Atlas, you can avoid having to write Javascript/ECMAscript and tying it into your ASP.NET application. The Javascript generated by the Atlas framework is cross-browser compatible.

The Official Atlas Site has more information and downloads.

The video/screencast Developing ASP.NET 2.0 Applications Using Atlas is a great introduction to this technology.