“A jailbreak for the iPhone 3GS. And it’s awesome. To get started right now, go to purplera1n.com. Download it. Make sure you have windows(but not 7), the latest iTunes installed, and an iPhone 3GS with 3.0 firmware. Connect your iPhone normally. Click "make it ra1n". Wait. On bootup, run Freeze, the purplera1n installer app. Hopefully you’ll figure out what to do from there. Best tutorial gets linked to from purplera1n site. This tool is beta. Make sure to have everything backed up before running. Also if Cydia doesn’t show up after running Freeze, reboot”
Do not upgrade to 3.1 yet if you want this unlock!
Here’s a brief video demonstration by @planetbeing of the iPhone Dev Team’s ultrasn0w unlock for the new iPhone 3G S. Special thanks to @Oranav for the at+xlog crash — a gift to the community that has kept on giving!
Our uses the at+xlog crash as an injection vector of our unlocking payload — and it does so on the 3GS in exactly the same way as on the 3G! But this injection vector will be lost if you update to 3.1 using the official Apple IPSW, which updates the baseband. So stay away from official 3.1 IPSWs until we release the tools that let you update the firmware without updating the baseband.