I found this Trendnet 54Mbps 802.11bg Wireless USB 2.0 Adapter. Trying to make my desktop wirefree, I got this. I was doubtful, but works flawlessly in ubuntu. You just plug and play. Supports WPA, WPA-PSK.
Microcenter is carrying a special on this one until Nov 1. You can get it for $7 (+tax).