To Unlock your iPhone 3G / iPhone 3G[S]:
1. Ensure you have upgraded to iPhone OS 3.0
2. Jailbreak your iPhone 3G / iPhone 3G[S] using RedSn0w or PwnageTool (this will also install Cydia).
3. Open Cydia.
4. Add this source to Cydia:

Code:

http://repo666.ultrasn0w.com

5. Search for UltraSn0w in Cydia and install.
6. Reboot your iPhone 3G / iPhone 3G[S].
Please Note: T-Mobile users should disable 3G before using UltraSn0w.