Windows Phone 7 handsets from Samsung have the ability to do USB tethering?
Although it doesn't look like it's able to be pulled off on any other Windows Phone 7 handsets aside ones from Samsung, it requires a quick and easy to do hack to enable using your fancy new smartphone as a 3G modem. Specifically, you'll need to pull up the dialer and punch in ##634# to launch the diagnostics menu, punch in *#7284# in the next menu, move over to the “Modem, Tethered Call” mode, and then pass through some additional prompts to get the automated USB tether completely activated.
So if you're sporting either a Samsung Focus or Omnia 7, you can give it a shot and see if you can get this much wanted feature enabled.
source: HDBlog.it (translated)