Any Belkin card from 2003 and earlier works great: in fact, some newer cards work. LimeiBook just bought one from Best Buy that works great, no drivers needed. It is a box that has a picture of a TiBook on the front.
I personally use Belkin 54g cards that are 802.11b but run a 802.11g speeds. F5D7010 is its model number. Or search Ebay for Orinoco. Any cards based on that chipset work.