iPhone 3G Unlocking Procedure
This is a very easy procedure to follow, no software or datacable required.
NOTE: You must jailbreak the phone for this to work, see the 3G jailbreak procedure if you haven't done so. T-Mobile USA users must disable 3G before using ultrasn0w.
NOTE: This is only for iPhone OS 3.0 - please upgrade if you haven't done so!
Run Cydia (the app installer that's present after jailbreaking)
Add repository repo666.ultrasn0w.com to Cydia. Make a note that it's the number 0, not the letter O.
Search for ‘ultrasn0w'and then install it.
Reboot your handset. It should now be unlocked and accept any SIM card!