http://www.amazon.com/SANOXY-USB2-0-Wireless-802-11-Adapter/...
If you want the whole computer instead of just wifi, try this:
http://www.volumerates.com/product/tp-link-tl-wr703n-openwrt...
OpenWRT preinstalled for your convenience.
That Ralink USB dongle looks like a great way to hook the Raspberry Pi up for internet, too.
http://www.amazon.com/SANOXY-USB2-0-Wireless-802-11-Adapter/...
If you want the whole computer instead of just wifi, try this:
http://www.volumerates.com/product/tp-link-tl-wr703n-openwrt...
OpenWRT preinstalled for your convenience.