Chronic Dev Team has released another iOS jailbreak. This one is for iOS 4.2.1 and is untethered, meaning you will be able to reboot your phone without connecting it to your computer first. Right now, this only works on Mac OSX.
If you are looking for a carrier unlock, this is not what you want. Make sure you hack STOCK 4.2.1 on your device before you bother trying this. It looks like the servers are crowded at the moment, so you might also want to wait a while before trying this out. I’ve also heard sprinkling the blood of a freshly killed chicken over your device will improve your chances.
Chronic Dev Team has finally released the much awaited GreenPois0n RC5 which brings full untethered iOS 4.2.1 jailbreak for all iOS devices. Unlike Redsn0w 0.9.7, GreenPois0n RC5 doesn’t require you to have SHSH blobs of 4.2b3 saved on Cydia. You can jailbreak any iOS device out of the box on iOS 4.2.1 using this latest version of GreenPois0n.
via Redmond Pie