Now jailbroken iPhones can be unlocked for use on other carriers using the SAM (Subscriber Artificial Module) package. The process works with the GSM iPhone 4 and 4S running iOS 5 and equipped with any baseband. This means that users looking to unlock their devices for use on a different carrier don't have to wait until they're out of contract.
The unlock comes thanks to Chinese iPhone developer Loktar_Sun. The SAM package can be installed by first adding the source repo.bingner.com to Cydia on a jailbroken iPhone. For instructions on how to add a repository to Cydia click here.