I've already got one WiShield from async_labs and am looking for another before they disappear. async_labs have closed their doors but made some great items for connecting to WiFi with an Arduino. I could also possibly buy one of their Black Widows (Arduino with built in Wi-Fi).
I have one async labs and i bought it second hand in pretty good condition in about 15 dollars so it was quite a steal , See there are other latest stuff for implementing wifi on a arduino like the sparkFuns Wifly shield you should go with this as the async labs libraries are stagnant and do not seem to get updates as the main people have closed down their labs and Wifly shield from sparkfun is something latest with library support and adherence towards Arduino 1.0.
Pauly:
The Wifly shield certainly is an option, but at $90 vs $55 I like the Asynclabs price better. Anyone know of any other WiFi shields available?
Your search on sparkfun seems to have missed a few options. Here is the $35 WiFly RN-XV. Use it with an XBee shield like one of these compatible shields.