Rob mentioned it here first and while I don’t normally re-blog other’s posts I thought this was significant enough to mention. 

I used to do this quite a lot with VSS – sharing files between multiple projects.  With VS 03 and VSS it was sort of necessary to do this because of the awkward way that VS creates VSS projects.  I haven’t had to do this with TS Source Control yet but I can see that it would be useful.

Of course, if your migrating a large VSS install to TFS then you may need to do this.