I've just successfully got going using Ubuntu on an old PC that was given to me a few weeks ago. Because the OS was a non-validating version of XP, I decided to try Ubuntu. I downloaded and installed Ubuntu, bought a WiFi card off of eBay and then set about to see if I could make it a WiFi machine. After many, MANY hours of failed attempts, this morning it works! If you're interested, here's the back and forth on the Ubuntu forum for how we set it up:
http://ubuntuforums.org/showthread.php?t=553862

-Bob
http://www.bobafifi.com
http://www.blogher.com/user/bobafifi/track