Atlas with any othe name is: Microsoft AJAX Library
For some of you who are still calling Microsoft AJAX, "Atlas" the name has changed.
Atlas is being split into three distinct products, with the server-side functionality now dubbed: ASP.NET 2.0 AJAX Extensions. The final versions are slated to ship by the end of the year. Atlas is designed to simplify the creation of ASP 2.0-based Web sites that take advantage of advanced JavaScript and XML functionality. On the client-side, the technology will be called the Microsoft AJAX Library, which integrates with the server-based Extensions. Microsoft has also renamed the "Atlas" Control Toolkit to the ASP.NET AJAX Control Toolkit. You can read more about it....
for further information you can also look at the ASP.NET AJAX Control Toolkit project page on CodePlex. CodePlex is Microsoft's community development web site. You can use CodePlex to create new projects to share with your fellow developers around the world, join others who have already started their projects, or use the applications on this site and provide feedback.
Have FUN!