iPhones 3G that was released last 11 June was bundled with AT&T providers. There have been many attempts to create a software that would be able to unlock the iPhones 3G so that it can be used with other GSM cards. "iPhone Dev team" has been working on find the ways to unlock the phone.
Some Brazilian teams have been releasing the iPhone 3G video proof on unlocking the phone. I read a blog as well that has been promoting a iPhone 3G unlocking software. Well, it seems that the developer has been better and better in predicting the locking rules/validations.