Geohot released blackra1n (jailbreak) and blacksn0w (unlock) for the latest firmware/baseband combo on 3G and 3GS iPhones for both Mac and Windows platforms!
Features of blackra1n RC3 :
- Jailbreak / Unlock
- Hacktivate or legit activation
- All Macs (Intel and PPC) and windows
- (Possible) Tethering option enabled

UPDATE : If you have 3.1.3 iPhone 3GS + 5.11.07 baseband and if blackra1n doesn’t work, try blacksn0w RC2 which can be installed by adding http://cydia.pushfix.info into Cydia sources. Please post a comment if you still have problems unlocking your 3GS.

Step by step instructions : …