Running iOS 6.1.3, 6.1.4.
Sure! Use P0sixspwn by iH8sn0w, winocm, and SquiffyPwn
Running iOS 6.0 through 6.1.2.
Running iOS 5.1.1.
Running iOS 5.1.
iPhone 4S, iPad 2, and the new iPad: nothing.
Running iOS 5.0.1.
Running iOS 5.0
iPhone 4S: redsn0w+corona. iPad 2: nothing.
Other devices: A tethered jailbreak is available.
Running iOS 4.2.9-10 or 4.3.4-5.
iPad 2: nothing.
Other devices: A tethered jailbreak is available.
Running iOS 4.2.6 through 4.2.8, or iOS 4.3 through 4.3.3.
Yep, you can use redsn0w.
(Or open JailbreakMe on the device itself.)
On iOS 4.1 through 4.2.1
Sure, just use redsn0w.
On iOS 4.0 through 4.0.2.