Visual Overload

I reached my record of running five concurrent instances of Visual Studio (four 2010, one 2008) recently. Seems like there should/could be a better way to have multiple solutions open at once, especially since each VS took about 500MB of memory each (with 8GB memory total, this wasn't really a problem, but it could be if I also had other high-memory programs open). Maybe one VS can have multiple solution-spaces open, like tabs, but at a higher level than the tabs for open files? Not sure, but it seems like a better answer is waiting for someone to discover it.