Connecting wirelessly to the internet is one of the greatest conveniences ever (up there with Micro Magic microwaveable French fries) and is usually pretty cheap. A wireless router now can be had for very little money and setup is a breeze. Connecting your Xbox 360 wirelessly, however, is still expensive due to an overpriced adapter. The adapter costs entirely too much to justify its convenience.
But, if you happen to already have a WiFi-enabled laptop, you may be in luck. Through a little trickeration, you can turn your laptop into a WiFi adapter. Instructables shows you how to do it.