Firecore, the developers of the aTV Flash software for Apple TV have now come up with a new product that will let users jailbreak their second generation Apple TV. Called Seas0nPass, the application would let users install custom IPSW firmwares for their Apple TV devices.
Please do note that at the moment, this is a tethered jailbreak. This means that you will need to connect the Apple TV to a computer every time you want to boot. Also, as with any jailbreaking process, deploying this tool could potentially brick your device and probably void your warranty. So, it goes without saying that you need to proceed at your own risk.
The Firecore team has posted a comprehensive how-to guide for the jailbreak process. You can check the tutorial here and please do let us know how the process goes in the comments below.