Start here: How do I jailbreak or unlock? How do I jailbreak iOS 5.0.1, 5.1, and 5.1.1?
No jailbreak for iOS 5.1 or 5.1.1 on iPhone 4S, iPad 2, or iPad 3rd generation; only a tethered jailbreak (redsn0w) for other devices.
You may be able to restore your device to iOS 5.0.1 using SHSH blobs - see this guide to downgrading or upgrading your device (including instructions for using the new redsn0w to downgrade iPhone 4S and iPad 2).
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