Just found this gem last night while reading through some VB team blog entries... I didn't know it existed, so I figured I would share with anyone who also is not aware of it.
In Visual Studio 2008, you can use ctrl+tab to bring up quick switch between any of the active (open) documents and even the active tool windows. It even creates small screenshots of the selected item. If you use alt+tab to toggle windows in your day to day computer use, then you will likely find this to be really useful in your VS development.