A few minutes ago the Dev Team published a new version of the redsn0w jailbreak program, and with its help you can do jailbreak for new iOS 6GM released last night. redsn0w 0.9.13 dev 4 jailbreak for iOS 6 on only 3 terminals, but it doesn't install either Cydia, so you can only use it if you absolutely want to jailbreak and use command lines to install tweaks/applications from Cydia. MuscleNerd says that certain plugins like PrefereneLoader are not yet compatible with the iOS 6 jailbreak solution, so you won't be able to use them.
Update #3 – Sep 13: The "dev4" version covers all the betas and yesterday's 6.0 GM seed. There are some remaining issues with Cydia and fundamental modules like PreferenceLoader, so it remains an openssh-styledeveloper-only release only for now!
You can download redsn0w 0.9.13 dev 4 available here and using this tutorial you can jailbreak, the only mention being that you can use an ipsw of iOS 6 GM for the procedure.
