If you are lucky enough to live in an area where Clearwire/ Freedom Pop services you, I would like to say that the Photon mobile hotspot works on the RPi.
You can just plug in the Photon to the RPi via usb and Wheezy automatically recognizes it and ifconfig shows it as usb0.
It doesn't however setup the networking automatically so simply typing in dhclient usb0 (or whatever else ifconfig shows the hotspot as) will get you an ip address and get you running.
I did run into an issue where I plugged in the Photon while the RPi was running and it restarted it. So I just turn on the hotspot, plug it in, then turn on the RPi