welcome to LQ!!
My approach is always to lobby the site admin to fix the site to work on--at least--Firefox. If they follow standards, it just happens.
Recognizing that you may not want to go on this crusade..
...here is more practical help:
Internet Explorer will run under WINE (or CrossOver, which is the commercial version). I highly recommend CrossOver--I am right now running IE6 using it and it seems to work fine. The advantage of CrossOver is the nice GUI installer and the support. They have a free trial available.