PDA.net will do likewise. I can tether to my Droid smartphone. It is a drain on the battery so best used while plugged in.
I use PDA.net on both our Mac and PC laptops, just no Linux binaries
With a 4G/LTE phone like the Samsung Galaxy SIII, I'm seeing 22M down, 6M up.
One trick we use when mobile is to plug in a voltage converter strong enough to keep the laptop charging , tether the phone, and then the phone charges over USB even as you are using it as as modem. It will get warm.
