Previewed at WWDC, launching in the fall.
Early Apple TV Jailbreak Opens Door to Apps
The new Apple TV was successfully jailbroken tonight which opens the door to further customization. The process of "jailbreaking" involves gaining full access to the device that allows developers to add new functionality to the device. The iPhone, iPod Touch and iPad have all been successfully jailbroken over time and has allowed individuals to install unauthorized applications to their devices. The original iPhone jailbreak even allowed 3rd party applications to be developed well before Apple launched the App Store. Some successful App Store apps such as Labyrinth and Tap Tap Revenge had their origins in the Jailbreak scene.
This video shows that they have accessed the new Apple TV:
Despite this early step, we're still many steps away from easily installing 3rd party applications to the Apple TV. Apple is also likely to be considering an official App Store for the Apple TV, though they've yet to announce any official plans.