We just released Visual Studio Team Foundation Server MSSCCI Provider Beta 2, which now includes support for using Team Foundation with both Visual Studio 6.0 and Visual Studio .NET 2003. This release works with Team Foundation Server RC, and should also work with the final released bits, too.
The Visual Studio Team Foundation Server MSSCCI Provider enables users of Visual Studio 6.0 and Visual Studio .NET 2003 to use Visual Studio 2005 Team Foundation Server Version Control with integrated source control features. This release includes support for work item integration to associate work items with changesets, and check-in notes.
See Brian Harry's post (An updated TFS MSSCCI provider is available) for further details.
For help using the provider, visit the Visual Studio Team Foundation Forum.