Pod2g has announced an untethered jailbreak for iPad 3 running iOS 5.1 with a quick demo video (embedded after the break).
Hey. iPad 3,1 running iOS 5.1 untethered. Next on the list: stabilizing the payload, then trying 5.1.1.
If it works on iPad 3 and iPhone 4, I can say it'll work on any device. The ATV3 may be out tho… :/