So you want to use the .NET 3.5 framework in a MOSS site?  Let Visual Studio do the work for you…

  • Start Visual Studio 2008 and create a new ASP.NET Web Application Project, targeting the .NET Framework 2.0
  • Copy the web.config of your SharePoint 2007 site, into the Web Application project in Visual Studio.
  • Open the Project Properties in Visual Studio
  • Select .NET Framework 3.5 in the Target Framework dropdown
  • Now copy the web.config from the Visual Studio Project back to SharePoint.

Gotta love it.