Today, Bob Bhatnagar from The iPhone FAQ says (in How to Activate iPhone Tethering With Firmware 3.1.2 (3G and 3GS)) Fortunately it's never been simpler to tether if your iPhone is running the latest firmware (3.1.2). Follow these steps to activate tethering, just keep in mind you are breaking all kinds of agreements with AT&T and Apple in the process.

And Adam Pash from Lifehacker says (in Enable Tethering on Your iPhone 3G or 3GS Running 3.1.2 [IPhone]) Jailbreak your iPhone with blackra1n (available for Windows and Mac).Unlock your phone with blacksn0w—which you can do through the blackra1n icon on your iPhone post-jailbreak.Install a custom IPCC file via mobile Safari.Turn on tethering in your iPhone settings. The MobileCrunch pos...

And Adam Pash from Lifehacker says (in Enable Tethering on Your iPhone 3G or 3GS Running 3.1.2 [IPhone]) AT&T has been dragging its feet on data tethering for months now, so if you're fed up waiting for official support and desperate to tether your iPhone's internet connection, weblog MobileCrunch...