James Newkirk has posted notice that an early build of his tool to convert your NUnit-based unit tests to Team System unit tests is now available on GotDotNet. (Note that this is currently only for C#, but that will change.)
I had the chance to speak with him at TechEd about the challenges involved and the technology he used to write the tool - interesting stuff! He is planning to release the source code, so I'm looking forward to seeing more of the implementation.
It's also good to see that he used the Guidance Automation Toolkit (GAT), another interesting product from the Pattterns & Practices team, to plug in to Visual Studio 2005.
-Chris