I saw this link on a new IE Tester. It looks like a really great idea. I only looked at it quickly, but I think it only runs on Windows. My big problem is that I don’t normally use Windows period and don’t have access to any version of IE.
Here are the links for the IE Tester:
Another option: run IE in Wine. You can have multiple Wine homes in which you could load multiple versions of IE. I know I have seen tutorials for loading IE6 in Wine, and I think just recently some tutorials for IE7 popped up.