From Codeplex:

Version 3.5.11119.0
2007-11-19 release of the AJAX Control Toolkit targets the official release of .NET Framework 3.5 and Visual Studio 2008.
  • AjaxControlToolkit-Framework3.5.zip is the full release package with complete source code to all controls, the test framework, VSI, and more.
  • AjaxControlToolkit-Framework3.5-NoSource.zip contains only the sample web site and VSI and is for people who don't need or want the source code for the controls.

http://www.codeplex.com/Release/ProjectReleases.aspx?ProjectName=AtlasControlToolkit&ReleaseId=8513