The website http://purplera1n.com, belonging to Ggeohot, offers a small windows-only application able to jailbreak an iPhone 3GS. You can then afterwards SIM-unlock it with Ultrasn0w.The iPhone DevTeam announced to be waiting for the iPhone OS 3.1 before releasing its jailbreak tool for the iPhone 3GS, as releasing earlier might have given Apple more room for building a stronger protection.
