iOS security researcher pod2g tweeted today that his iPhone 4 running iOS 5.1 is now running untethered. Though he has not released it yet, but we expect a redsn0w update to come out soon which will make it available for the masses.
He is also running a Poll to hold on the jailbreak for iOS 6 here
pod2g has put a lot of work into something to the jailbreak community for free. If you happen to run into him on Twitter, feel free to show him some love.