Geohot released his own jailbreak tool named Purplera1n. At the moment this tool is available for Windows only, Mac version is expected to release on coming monday. Before getting started let me confirm you Purplera1n is for jailbreaking only you can’t do a unlock with Purplera1n. This tool is totally different from Quickpwn or Redsn0w. And very little in Size so there is no need to put your phone in DFU mode at any instance of time during the jailbreak operation.
1st Downloadclicking the Windows logo appears on the site;
2nd make sure you have the latest version of iTunes installed (iTunes must remain closed during the jailbreak) and the 3.0 firmware on your iPhone 3GS;
3rd Connect your device to your computer;
4th Start purplera1n and click the “make it ra1n”;
5th Wait until the application doing its work and that the device is restarted;
6th Freeze icon will appear on your Springboard.Do a tap on the Freeze to install Cydia (requires WiFi or Internet connection);
7th Cydia If not there, Geohot recommended to restart “Freeze”.
Screenshots Via iSpazio
Update : Peoples are getting errors and Winterboard is not supported by this release. PurpleRa1n is still in Beta version and we are expecting a new release on Monday. So if you are not in a hurry then you can wait for next Ra1n or Dev team release after the final 3.1 firmware from Apple.
Unlock Update : Folks over different forums confirmed that current Ultrasn0w is capable of Unlocking the Jailbreaked iPhone 3G S with Purplera1n. So we don’t need new repo or new tutorial so i modified my 3G guide so enjoy new Unlocked iPhone 3GS with Ultrasn0w. How to Unlock Your iPhone 3GS OS 3.0 With UltraSn0w