News of an untethered jailbreak for Apple's iPhone OS 5.1.1 has been circulating for at least several days, but this morning iOS hackers managed to release the fruits of their labor: Greenpois0n's Absinthe 2.0.x. If you're curious, the press release (yes, a press release) can be found here. The untethered jailbreak tool works on virtually all iPhones and nearly all iPads, including the iPhone 4S, iPad 2 and the iPad 3. The tool does require that the device already have 5.1.1 loaded, so make sure your iOS device is up to date before beginning.
The blog post claims it's "so easy your grandma could do it", but there do exist a couple of caveats to this release, aside from the usual dangers.
Firstly, it almost works for all iOS devices -- almost. Over the past few days, support for newer devices has been continually added and tested. Although the list of supported devices is indeed extensive, Greenpois0n's website explicitly warns users that Absinthe 2.0 will not work for AppleTV 3. Other sources are also reporting that Absinthe has one more problem area: the newly updated iPad 2. Also known as "iPad 2,4", the tablet is a rehashed version of the iPad 2 with a lower price and a new 32nm processor.
Secondly, the target device must be running 5.1.1. Absinthe 2.0.x works on this version exclusively so if you're running an older version of iOS, you'll need to update first.
For those of you already running iOS 5.1.1 with a tethered jailbreak, you can snip the cord by checking out Rocky Racoon 5.1.1 Untether tool at CydiaHelp.