Now that the iOS 4 jailbreak has been released, those of you who were waiting for an unlock can unlock their iPhones with UltraSn0w. Before getting into the details, let me tell you more about who this is for and who this is not for.

The latest version of ultrasn0w will unlock the iPhone 3G and iPhone 3GS running iOS 3.1.2 or higher. As long as you are running iOS 3.1.2 or up to 4.0.1, you’re good.

This being said, ultrasn0w will not unlock the iPhone 4 at the time being. The Dev Team needs a little bit more of time to test out the iPhone 4 unlock before releasing it. I believe they will release the iPhone 4 unlock in the next few days, so stay tuned.

This guide and tutorial will show you how to unlock your iPhone 3GS or iPhone 3G running iOS 4 using ultrasn0w.

Step 1: Make sure your iPhone is backed up in iTunes.

Step 2: Jailbreak your iPhone using JailbreakMe (see instructions here).

Step 3: After the jailbreak process is done, go to Cydia and search for ultrasn0w.

Step 4: Install ultrasn0w and reboot your iPhone.

Step 5: Done!

You now have an unlocked iPhone 3G or 3GS.