iTether is an iPhone app that allows users to share their iPhone's internet connection with their Mac or PC computer over USB. However, the application was available for only a few hours on the App Store before Apple removed it over "carrier concerns".
There are two parts of the iTether app -- an iOS app and a computer-side application. Though the iOS app isn't available for sale anymore, Tether continues to offer updates to the computer-side apps. The company has released an update to the Mac client to fix a crashing problem under OS X Lion that a number of users have experienced.
The update can be downloaded from Tether's website.