I bought a Belkin ADSL modem and 802.11g router which came bundled with a USB wireless dongle. I wanted to use it with my iBook, which would take an original AirPort card, but why waste what I already have? After much searching and trying many possible solutions and modifiying countless plist files, I stumbled across a forum with a link to a driver download page for a list of wireless cards, and includes a driver for OS X 10.4 -- scroll down to the Mac section and find the USB driver for 10.4. This link (492KB) should download the current driver, dated August 28, 2005. There are drivers for 10.3 there as well.
I installed it and it worked the first time -- although I did need to switch off Tx Burst mode in the Advanced settings, and turn off IP6 in the Network System Preference. Enjoy!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050826105609733