Pod2g, the hacker behind the iOS 5.0 and iOS 5.0.1 untethered jailbreaks, has revealed that a public jailbreak for A5+ iOS 5.1 devices is at minimum weeks away.
Pod2g has asked the jailbreak community to send him any iOS 5.1 crash reports that are reproducible to assist in finding a jailbreak for the new firmware version.
These are instructions on how to jailbreak your iPod Touch 3G and iPod Touch 4G using Greenpois0n for Windows. Greenpois0n supports iOS 4.1 and iOS 4.2.1.
Instructions on how to jailbreak and unlock your iPhone 3G on the iOS 4.2.1 firmware using RedSn0w for Mac. This tutorial can update your baseband if needed for unlock.