The Pwnage Tool by the DevTeam hacker group allows you to create custom iPhone firmwares for the purpose of jailbreaking, to get full control over your device (see why you should jailbreak here).
George Hotz a.k.a GeoHot has released blackra1n RC3, which is an update to a 1-click jailbreak that adds activation options and an add-on blacksn0w, which unlocks latest iPhone 3G and iPhone 3GS ...
We’ve seen videos of iPhone 4.0 Beta being jailbroken, but we thought we’d have to wait for quite a while until the jailbreak tool is released. Well, surprise! It’s already available for iPhone 3G ...