[UPDATE: And, just like that, it's gone! I told you to be quick!]
It seems that Apple has approved a USB tethering app for the iPhone, iPad and iPod touch.
The app is called iTether and is available for $14.99. No jailbreaking required!
I've been able to try this app out and it does exactly what what it ways on the tin. Seems to work very well.
Tether has previously released tethering software for BlackBerry and Android.
According to a post made on Twitter by Tether, the company got this into the App Store because it 'played by the rules.'
The app is already the #1 top grossing app in the App Store and #3 in the UK.
Not sure whether this one slipped through Apple's net or it's a change of policy (I'm betting it's the former, not the latter), but there's a good chance it won't be available for long, so if you want it, go get it!
A WORD OF WARNING: Unless your data plan specifically allows tethering, chances are using this app will violate the carrier's terms and conditions. I point you to this excellent piece by James Kendrick to explain.
Thanks to everyone who sent me a link to this!