In Pictures: A sneak peek at Apple's upcoming OS X...
OS X Mountain Lion can send a 720p video stream of what's on your Mac's screen to your HDTV via a second-generation (black) Apple TV. When a Mac with a second-generation Intel Core processor running Mountain Lion senses the presence of an Apple TV on the local network, an AirPlay icon menu appears in the menu bar. Click it, choose Apple TV, and you're mirroring your display -- no cables required.
In Pictures: A sneak peek at Apple's upcoming OS X Mountain Lion