As the title says, it's out people... go get it.
Just used it, and we are untethered! Yay
For info, the same rules apply to this as did for redsn0w if you are on Vista or Windows7.
You need to run it under compatibility mode for "Windows XP Service Pack 2" and with administrator privileges.
Sorry for not linking originally, I just guessed everyone would be able to have a stab at it... http://www.greenpois0n.com/
If you are already JB tethered with redsn0w you can simply run greenpois0n OVER THE TOP. No need to restore. It will simply untether your existing jailbreak!