Don't want to spend a ridiculous $100 on a simple wireless connector for your XBOX? (Shees, an entire XBOX can be bought for $199!)
Anyway, find an old router laying around and load a Linux hack onto it's BIOS, and create a wireless bridge from this hacked router to your wireless internet router.
Used routers are about $20 or less...
http://www.cellfanatic.com/2008/01/13/router-dd-wrt-low-cost-xbox-360-wireless
http://www.geeksaresexy.net/2007/10/02/how-to-cheap-wireless-for-your-xbox-360/
http://www.dd-wrt.com/wiki/index.php/Main_Page
Geek out,
Matt