Unlock iPhone 3G with fireware 3.0

How to unlock an iPhone 3G using ultrasn0w
1. Find the Cydia application on your iPhone’s SpringBoard.
2. Tap on the Cydia icon. This will open the Cydia application.
3. Select the Manage option on the lower menu bar.
4. Here you will see two options; Packages and Source. You will want to select the Sources option.
5. This will bring you to the list of sources that are already installed on your iPhone or iPod Touch.
6. To add a new source, select Edit in the upper right corner.
7. Now select Add in the upper left corner.
8. This will bring up a pop-up in which you can enter the url for the source. Do not delete the http://. Just begin typing the url after the http://. The source url needs to be typed into your iPhone/iPod Touch perfectly. The source url is repo666.ultrasn0w.com. The o in snow in actually a zero. If you put on o, it will not work.
9. Once the url has been entered, select Add Source.
10. Wait for the sources to update. Once the sources are finished updating, select the Return to Cydia option at the bottom of the page.
11. This will bring you back to the list of sources. Select Done in the upper right corner.
12. The source has now been added to your sources list. Tap on the repo666.ultrasn0w.com source.
13. Select the ultrasn0w application.
14. Select Install in the upper right corner.
15. Select Confirm in the upper right corner.
16. Wait for ultrasn0w to install. Select Return to Cydia.
17. Restart your Device (hold power and home button at the same time).
18. Your iPhone will now be unlocked. You can remove the SIM from the top of the device and insert a new one. You may need to restart your iPhone after inserting the new SIM. Below are screenshots of an iPhone with no service, no SIM, searching for service after inserting the new SIM and finally the iPhone with service after inserting the new SIM.