Switching between Team System and SourceSafe
During our migration period, we are currently using both Visual SourceSafe 2005 and Team System for source control.
You can switch Visual Studio source control providers "on the fly" via the
Tools, Options, Source Control, Plug-in Selection dialog:

And if you're like me, you keep forgetting to switch back, and wondering "Gee, why aren't my Team System source control menus appearing?" Doh!