Hacked.com has posted a how-to on getting your Xbox some 802.11 internet. From the article: "In this tutorial, I will show you how to install a wireless game adapter into your Xbox internally so that you can have a wireless connection, where available, without the extra hardware." This probably voids any warranty, but here's the needed items to get the job done:

* Xbox (Modded or unmodded)
* 1 - 8" 4-Pin Power Cable Splitter
* 1 - Netgear WGE-111 Network Adapter
* Torx-10 and Torx-20 Driver
* Soldering Gun
* Solder Braid
* Solder Patience

Follow the link for the full tutorial.