Yesterday Microsoft announce a pre-release an upcomming power tool called TFS Migration and Synchronization Toolkit, you can download it here.
The toolkit aims to help people with the migration towards TFS and offers a set of apis to make life easier for people with heterogenous systems by helping with bi-directional syncronization. Be sure to check it out and remember to be share your solutions (CodePlex is a great place for this) my guess is we'll be seeing some nice integration tools soon.
And a quote to rember when playing with this comes from Matthew Mitrik:
Please note that this is a prerelease version of the Migration and Synchronization Toolkit. Several features are not complete and as testing has not completed, the code has the potential to contain bugs and overwrite data stored in TFS. Please be careful to use this only in a testing environment and not on live production data.
Another one from Robert Horvick:
Oh - and this is still under active development (and has known issues) so if you have any feedback it's still early enough for it to be considered for inclusion in the final drop.