Jailbreak iOS6 beta 1 using Redsn0w 0.9.13dev1
Just days after the seeding of iOS6 beta 1 to Apple developers, the iPhone-Dev team has released Redsn0w 0.9.13dev1 to perform a tethered jailbreak on iOS6 beta 1 using GeoHot's limera1n exploit(A4 devices and lower only). However, this release is for developers only. First of all, you need a developer account in order to restore the iOS6 beta firmware anyway and secondly, this jailbreak will not install Cydia. It will, however, give you root access to the device via SSH or afc2.
The first time you run Redsn0w, you will need to specify your 6.0 beta 1 IPSW file. This is because the firmware is only available through the developer portal, so Redsn0w cannot yet fetch the files needed from within the program. After you run the jailbreak for the first time, Redsn0w will cache the files needed and you will no longer need to specify firmware from that point forward. Remember, this is a tethered jailbreak so you will have to use the "Just Boot" option every time you reboot the device in order to use Safari, Cydia, etc.
Again, we must stress that this jailbreak tool is for developers only. Cydia has not been updated to support the new SDK and many(most) apps are incompatible with iOS6. This jailbreak should only be used by those who develop 3rd party apps and want to begin adding support for iOS6 to their packages.