iOS 6 already receives a jailbreak for developers via redsn0w
The iPhone Dev Team has released redsn0w 0.9.13dev1 which will jailbreak iOS 6. This version of redsn0w only supports the iPhone 4, iPod touch 4G, and iPhone 3GS, namely no support for A5 devices. It will be a tethered jailbreak and should only be used by developers as it's a beta and you'll most likely run into issues.
If you're a developer running iOS 6 redsn0w you will have the ability to test your jailbreak apps. MuscleNerd has posted a warning on Twitter about non-developers running the new redsn0w:
redsn0w tethered iOS6 jailbreak for 3GS and A4 devices is.gd/MCbq7A (developers ONLY please! .. no Cydia, just SSH+afc2)
This basically means you'll be jailbroken but won't have direct access to Cydia. In order to install and access your file system you'll have to use the SSH method. This will give developers the access they need to make sure their apps are compatible with iOS 6 when an official jailbreak tool drops for the public version of iOS 6 that is scheduled to come out this Fall.
If you're currently on iOS 5, you can enjoy an untethered jailbreak on all iOS devices. Check out the additional resources below to get up and running on a current jailbreak. If you're a jailbreak developer, make sure you check out our jailbreak developer forums to converse with other developers on developing for iOS 6.