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Download From : http://UltimateJailbreak.com

From Where you can access iOS 5.1 Jailbreak then you have to read furthur more about it.

Apple iOS 5.1 Apps and Jailbreak Official Website : http://UltimateJailbreak.com

Apple Software Update iOS 5.1 Compatibility:
iPhone 3GS
iPhone 4GSM Model
iPod Touch 3rd generation
iPod Touch 4th generation
iPad
iPad 2

The following steps will help you jailbreak your device on Apple iOS 5.1

Step 1: Go to www.apple.com and Download latest iTune v 10.2.1 and Update your device to Software Update 5.1
Step 2: Then go to http://UltimateJailbreak.com and Download iOS 5.0.1 Jailbreak for Mac or Windows
Step 3: Save the iOS 5.1 Jailbreak Tool on desktop and Run as Administration
Step 4: Select your device and click on jailbreak button.