I have been using the IEs4Linux system for a while now to assist in developing websites. It allows you to install various versions of Internet Explorer in Linux. It’s great for testing websites against the many bugs in IE as you develop them.
Recently they have developed a version for OSX on Intel machines.
You have to install Darwine and X11 on OSX to use it, but after that it seems pretty easy. I am not so fortunate as to own an Intel-based Mac, so I can’t test it for you.
Wine on OSX info