So you can’t tether the iPhone? Not what 9to5mac says as they have now posted a How To Tether an iPhone for free, and without any AT&T blessing as well.
What you do require though is iPhone OS 3.0 Gold Master firmware carrying the “7a341” label and no doubt a quick search will show where that can be gained from, and once it is installed it will only take a few clicks to tether up your iPhone.
The tethering hack works on the iPhone 3G so hopefully will work on the new iPhone 3G S. The guys over at 9to5mac have an easy to follow guide on just how to achieve it so hit up the link and get tethering.