Here is a site that I always keep handy....
At the bottom there is a show all link that will bring up a huge list of wireless cards. Find a brand with the right interface for you (cardbus, PCMCIA, or USB probably) and see if it supported at all. Beware though, as wireless cards seem to have a habbit of changing the chipsets without changing the model numbers (in fact, the last time I looked at a wireless adapter, it said that right on the box), so the info on the page may not be entirely accurate.
A friend of mine got an external wireless adapter for a PS2 or XBOX that you set up on a windows machine, then it would work on anything with a working ethernet port. It was supposed to be an easy solution for using wireless with linux, but I don't think he has gotten around to trying it yet, so I can't tell you if it worked or not.