iOS 8 Jailbroken, We Recommend Holding Off for Now
The same team who released the kind of sketchy iOS 7 jailbreak has released a jailbreak for iOS 8.1. Currently, it's Windows-only, in Chinese, and doesn't install Cydia by default. You should probably wait to install it.
This jailbreak came as a bit of a surprise and subsequently it's a little rough around the edges. Users have reported that using a passcode crashes the system, a number of problems with Cydia, and a wide number of tweaks don't work. Cydia's been updated, but requires a manual install over SSH.