Jailbreak iOS 4.0.1 iPhone 3GS with PwnageTool (Unofficial Release)
There is now an unofficial version of PwnageTool out in the wild which can jailbreak iPhone 3GS (with old bootrom and already pwned on 3.1.2) on the latest iOS 4.0.1 firmware. The creators of the original PwnageTool has confirmed that this version has been modified and redistributed without their permission, and most importantly, it doesn’t patches some important files which are required for the ultrasn0w unlock to work properly.
I haven’t tried this tool, and wont recommend using this. I have posted this for informational purposes only. But if you want to give it a go, you can do so at your own risk by finding the download link here: (http://www.megaupload.com/?d=700HE23I). Also, iPhone 3GS users who are jailbroken using Spirit on 3.1.3, and with new bootrom should avoid upgrading to iOS 4.0.1 until new jailbreak tools are available.
If you are an iPhone 3G user, you can follow the complete step by step guide posted here to jailbreak your iOS device using Redsn0w, and then unlock it using Ultrasn0w 0.93 on any baseband (including 05.13.04 and 05.12.01).