Edimax EW-7811Un 150Mbps 11n Wi-Fi USB Adapter, Nano Size Lets You Plug it and Forget it, Ideal for Raspberry Pi, Supports Windows, Mac OS, Linux

Supports 150 Mbps 802.11n Wireless data rate - the latest wireless standard. Permits users to have the farthest range with the widest coverage. (Up to 6 times the speed and 3 times the coverage of 802.11b.).
Power Saving designed to support smart transmit power control and auto-idle state adjustment
Supports WMM (Wi-Fi Multimedia) Standard so that you can let different types of data have higher priority. It would allows better streaming of real-time data such as Video, Music, Skype etc
Includes multi-language EZmax setup wizard
Spec Standards IEEE 802.11n; backward compatible with 802.11b/g Wi-Fi Certified. Security 64/128 bit WEP Encryption and WPA-PSK, WPA2-PSK security; WPS compatible IEEE 802.1X
Port 1 x 2.0 USB Type A. Wireless Data Rates Up to 150 Mbps. Modulation OFDM: BPSK, QPSK, 16-QAM, 64-QAM, DSSS. Frequency Band 2.4GHz - 2.4835GHz. Antenna internal chip antenna
Channels (FCC) 2.4GHz : 1~11. Power Input USB Port (Self-Powered). Dimensions 0.28" x 0.59" x 0.73". Temperature 0 -40 degree C (32-104 degree F). Humidity 10 ~ 90% Non-Condensing. System XP/Vista/Win7, Mac, Linux