Amazon has the Linksys Wireless-G Game Adapter for less than $62 shipped:

http://www.amazon.com/exec/obidos/AS...413845-7285705

Works with both 802.11b and 802.11g networks. Works with XBox, PS2 and Gamecube with no drivers needed. Cheapest I could find on Pricegrabber was over $100, so this is a nice deal. I can confirm that this works great with XBox using the traditional Wireless-B network, so you don't need to get new equipment