In short: if you're at the University of Michigan, you can do cross-browser testing with Virtual Sites.
Disregard this post if you're not at U of M.
I'm a University of Michigan student and I sometimes need to do cross-browser testing, and I don't use Windows. The solution: Michigan offers Virtual Sites, where you can take control of a computer and test stuff out.
To do this, you'll need Microsoft's Remote Desktop Connection. If you already use Windows, you already have it. If you're on a Mac, you'll need to download it. I don't know of a Linux solution, sadly.
Once you've done that, configure your virtual session. You can see which version of IE you'll be testing on by checking the software list. If you've a CAEN account, you can also take control of a CAEN machine. As of this writing, the standard one has IE8 and the CAEN one has IE9.