The Dev-Team launched its long-awaited iPhone 3G unlock, dubbed "yellowsn0w," and while they're still working out a few kinks, reports are already pouring in of successful unlocks. It's also been confirmed that this release will work with the iPhone's latest v2.2 firmware, and in fact requires that the phone be updated to v2.2 to run at all.
The team also noted, "The iPhone 3G is used all over the world with all sorts of SIM cards, and we almost certainly will see untested and unexpected situations. If the soft unlock doesn't work for you on day 1 (literally day 1, of 2009!) then please don't panic or be impatient. This is new territory for everyone, so enjoy the ride as much as you can."
More info: Official Announcement