blacksn0w along with blackra1n RC3 were released earlier today which can jailbreak all iPhone’s & iPod touches, and can unlock iPhone 3G/3GS running on 3.1.2 firmware with 05.11.07 baseband. You can follow the following step-by-step tutorial/guide to unlock your iPhone 3G and iPhone 3GS with the latest iPhone 3.1.2 firmware using blacksn0w from Cydia. This unlocking guide applies to iPhone 3G and 3GS users who were already jailbroken on 3.1.2 firmware using PwnageTool 3.1.4 instead of blackra1n. Those of you with iPhone 2G should follow the guide posted here or here for unlocking and jailbreaking 3.1.2 firmware.
The popular iPhone hacker Geohot has finally released the much awaited blackra1n RC3 with blacksn0w which unlocks both iPhone 3G and iPhone 3GS running on iPhone 3.1.2 firmware with 05.11.07 baseband (aka modem firmware). This latest version of blackra1n includes unlock and jailbreak for 3.1.2 firmware on 05.11.07 baseband, option for enabling native Internet Tethering on the iPhone, hacktivation support, 15 seconds speed improvement and support for OS X Tiger & PPC (PowerPC) Macs. However it is to be noted that blacksn0w is for iPhone 3G and 3GS users only. Those of you with iPhone 2G should follow the guide posted here or here for unlocking and jailbreaking 3.1.2 firmware. Here is a complete step by step guide on how to unlock iPhone 3G and 3GS running 3.1.2 firmware on 05.11.07 baseband with blacksn0w.