iOS 5.1.1 is out now. While it's mostly usability upgrades and bug fixes, you may as well upgrade if you can. As usual, the Redsn0w jailbreak tool is ready pretty much simultaneously, and Redmond Pie has a walkthrough for how to install it.
Like all tethered jailbreaks, you'll have to boot your device into tethered mode every time you restart. If that sounds like a huge pain, maybe hold off for the untethered release, which is usually out a few days later, a week or two at most.
For newer devices, you'll have to wait. The hardware defect in the A4 devices means that the crack can come literally minutes after jailbreak devs get their hands on a new iOS update. But finding a way into the newer devices, like the iPad 2 and the iPhone 4S is a lot tougher and more time consuming. [RedmondPie]