Officially, thethering is not an option with the iPhone 3.0 for most AT&T customers in the U.S. Well, there’s an easy tweak to enable this feature in a matter of seconds, the problem is that AT&T and Apple don’t support this tweak so use at your own descretion. Oh, and there is no guarantee that this will work…
1. Download this carrier update file from Wired. Then extract it.
2. Launch the Terminal app and type the following command:
defaults write com.apple.iTunes carrier-testing -bool TRUE
 

3. Now launch iTunes. In the iPhone window,  …

AT&T has announced new data plans for the iPhone, iPad and other smartphones on its network. In addition, the iPhone will get data-tethering when the iPhone OS4 update hits this summer.
The new plans are rather simple. DataPlus gives you 200 MB of data per month for $15 (and you can add an extra 200 MB for another $15). DataPro cuts you from the 5-GB “unlimited” plan to 2 GB and it will cost $25. Get an additional 1 GB for another $10.
To tether your phone and share its data connection …