If you have a mac, the usb solution is a bit more difficult. There is an answer.
Use a D-Link DWL-G122 USB WiFi Dongle - revisited
D-Link made one two years ago, but its new version (the DWL-G122) doesn't support OS X any more. So I came across a one-year-old hint here, which made me purchase it, because the hint (and replies) stated that "rev B1" of this dongle used a chipset that was Mac-compatible ... and that the maker (Ralink) had an OS X driver available on their site.
Below are links and demos on how to make and use one..
