Just released (or should I say, prereleased) tonight on Codeplex, the TFS Migration and Synchronization Toolkit (the toolkit) Prerelease.  See here. We've be working on hard on this toolkit to make availalbe the best practices  we have learned from migrating and synchronizing millions of files and work items internally and for customers.  If you are thinking of migrating from an existing version control or work item tracking system to TFS, you'll definitely want to check this out.  Let us know what you think.