The guy behind StealthBravo has managed to modify the latest AT&T Carrier Update file v6.0 so that it enables MMS and Tethering functionality on iPhone firmware 3.0 or 3.0.1. This will only work for AT&T customers with iPhone 3GS/3G running firmware 3.0.1/3.0.
The wait is finally over! MMS feature has finally landed officially for AT&T iPhone users - a feature which almost every other phone has had it for years. It comes in the form of a small (a few kilobytes) carrier update (.ipcc) file for iPhone 3G and iPhone 3GS users which makes the update painless as you don't have to download a whole new firmware update just to gain this functionality.