Older version of iPhone the 3G has just been unlocked and this happened some four hours before press time. The guys from Dev team have released their ultrasn0w software and we can confirm that after applying this to a jailbroken iPhone 3G with software 3.0 works.
This even unlocks the phones with previously un-unlockable 2.30.03 baseband and since software 3.0 upgrades your baseband anyways, we got multiple confirmations that this works. If you want to dare and unlock your iPhone 3G with 3.0 sofware you can find all you need here. If you still own an iPhone 2G, then the phone was already unlocked with a jailbreak.
If you are waiting for an unlocked / jailbroken iPhone 3GS, unfortunately you will have to wait a bit more, as there are no any reports that this will be possible anytime soon.