Earlier today, Apple announced the developer preview for OS X 10.8 Mountain Lion. OS X 10.8 offers a number of new features we've detailed before.
InsanelyGreatMac has put together this nice walkthrough video of OS X AirPlay mirroring. That feature allows you to transmit your OS X desktop onto your Apple TV over Wi-Fi:
Article Link: Video Walkthrough of AirPlay and Other Features in OS X Mountain Lion