The iPhone Dev-Team has announced RedSn0w 0.9.15b1 which brings numerous new features including the ability to restore to older firmware not being signed by Apple.
The PanguTeam has released an updated version of its untether for the iOS 8.0 - 8.1 jailbreak, fixing an issue which could cause applications (particularly Safari) to randomly crash.
The PanguTeam has released an updated version of its untether for the iOS 8.0 - 8.1 jailbreak, fixing an issue which could cause your device to overheat due to excessive CPU usage.
Saurik has released an iOS 8 compatible version of Cydia for manual download following the release of an untethered Pangu jailbreak for iOS 8 - iOS 8.1.
These are instructions on how to jailbreak your iPhone 3GS and iPhone 4 using Greenpois0n for Mac. Greenpois0n has been updated to support the iOS 4.1 and iOS 4.2.1 firmware