I've had a tough time finding a usb wifi module that doesn't use an RTL 8xxx chipset. However the Edimax EW 7811UN N150 works great if you install the correct driver which I found to be non trivial without the assistance of this guide:
sites.google.com/site/easylinuxtipsproject/reserve-7
One thing to note, in my experience if you simply plug in the edimax and it seems to connect and function, look at the blue led. If it's on steady that's a tell tale sign the wrong driver is installed which will cripple the speed and cause hangups. Once the correct driver is installed all mine have blinked rapidly. I've used a half dozen of them on Wheezy and 2 on Mint with good results.
To achieve max range it seems to like to be installed into a powered hub, a short extension cable or in a usb port that doesn't have too many other items connected to the same internal hub.
