Blacksn0w has already been released by GeoHot on November 4th. For those who don’t know anything about blacksn0w, it is an unlocking tool developed by popular iPhone developer GeoHot. It helps iPhone to unlock baseband 05.11.07 on iPhone 3.1.2 firmware.
I have already posted a simple guide to jailbreak the iPhone firmware 3.1.2 using blackra1n RC3. You can use this guide to jailbreak your phone and then use following guide to unlock the latest firmware.