Adafruit Industries Adafruit Industries USB WiFi 802.11b/g/n Module with Antenna for Raspberry Pi
Make your Internet of Things device cable-free by adding super WiFi. Take advantage of the Raspberry Pi and Beagle Bone's USB port to add a low cost, but high-reliability wireless link. We tried half a dozen modules to find ones that work well with the Pi and Bone without the need of recompiling any kernels: its supported by the Bone's Angstrom installation that comes with each Bone as well as the Adafruit Occidentalis distribution. You'll have wireless Internet in 10 minutes! Works great with 802.11b/g/n networks.
Adafruit Industries USB WiFi 802.11b/g/n Module with Antenna for Raspberry Pi
Usually ships in 1-3 business days.