Update: For iPhone 1st generation / 2G running 3.1.2 go here.
Here are the steps to jailbreak and unlock iPhone 3G/3GS running on OS 3.1.2 modem firmware v 5.11.07 with blackra1n:
Before starting these steps, make sure you’ve updated to OS 3.1.2 from iTunes
While the iPhone Dev team waits for Apple to release firmware v3.1 before they unveil their iPhone 3G S jailbreak+unlock, George Hotz has gone ahead and released a jailbreak tool for the 3GS.
The jailbreak took is available via http://purplera1n.com/ and works on windows with latest version of iTunes (a mac version is expected soon). This [...]
The iPhone Dev Team confirms that the iPhone 3G S won’t be spared. Redsn0w & Ultrasn0w’s updated version will crack the 3GS easily – using the same exploit that jailbreaked the iPod Touch 2G.
Apparently Apple has left out a loophole in iPod Touch 2 (which is now repeated in iPhone 3GS) that lets the Dev [...]