Blacksn0w Alternatives
Blacksn0w is described as 'unlocks your jailbroken iPhone, allowing it to be used with any GSM carrier (AT&T and TMobile in the U.S.) without a contract. It can be installed through blackra1n, the jailbreaking application by geohot' and is an app in the system & hardware category. There are 2 alternatives to Blacksn0w for iPhone. The best alternative is Ultrasn0w, which is free.
Unlock your jailbroken iPhone with ultrasn0w, available from Cydia.
No screenshots yetBootNeuter will unlock your jailbroken iPhone 2G (running iOS 2.x or lower). It is available in the Cydia app store.