Ultrasn0w for iPhone 3G is ready!
- Ensure you have upgraded to iPhone OS 3.0
- Jailbreak your iPhone 3G using redsn0w or PwnageTool (this will also install Cydia/Icy)
- Run Cydia or Icy
- Please add the repo repo666.ultrasn0w.com to Cydia or icy
- Search for ‘ultrasn0w’ in cydia or icy and install ultrasn0w
- Reboot your iPhone 3G

Source :Â http://blog.iphone-dev.org/post/128573459/ultras-now