AUT - Auto USB Tether is an utility app that automatically activates your USB Tethering functionality whenever you connect your device to a PC/Mac through an Usb cable.

Gianluca Barbaro (AUT's Developer):
I decided to develop AUT after unsuccessfully trying the 10+ apps on the Play Store that claim to do what AUT does. None of them worked on my device or they were too complicated to use. Auto-activation of Usb tethering is not supported by the Android system, so it's not a surprise that those apps didn't work. It is a complicated matter from a developer's stand point.
With AUT I tried a different approach: auto-detection of the necessary parameters. It's not guaranteed to work on any device, but it definitely has more chances than apps with hardcoded parameters. Give it a try!

AUT can also show the current USB In/Out networking traffic and (attempt to) hide your tethered traffic from your carrier.