Let’s keep it short and sweet, the Dev-Team has come up with a new Redsnow version that will be more than happy to jailbreak any iOS 4.2.1 device.
However, the jailbreak is still “tethered” and jailbroken devices will still have to be plugged into a computer and booted in jailbreak mode if they lose power or reboot.
The jailbreak also doesn't support 3G and 3GS devices in the current build, but support should be added soon. Also, the iPhone 4 is expected to get a provider unlock soon as well.
You can check it out here.