Openwith.org offers Free programs to open any file extension! — something so useful I'm linking to it in this post so that I can find it when I need it.
(spotted via sexist pigdogs at Lifehacker: OpenWith.org Tells Your Mom How to Open That File (For Free))
This totally comes in helpful when you have clients sending you all types of different files, and they get angry at you because you don’t have the same obscure program they do. sheesh. : )