If you are looking to mirror a device on your Mac screen here is a good option, to start with. AirServer is an Airplay receiver for Mac/PC. It allows you to receive Airplay similar to an Apple TV so you can stream content or mirror your display from your iOS.
Most PowerPC users and some Intel Dual Core users really would like to have AirPlay to mirror Videos to our Apple TV without having to convert and sync with iTunes.
AirFlick is a beta version and there is no support but it works (sort of) on PowerPC. AirFlick is a free application that allows you to stream videos from your computer to Apple TV. Apparently, you’re also supposed to be able to stream videos from any URL address.
The fact is I recently updated my Apple TV and then I tried to use this application and for some reason it does not recognize my Apple TV, likely because of my upgrade. But I saw some comments online which indicate that it seems to be working for some of you, but some users experience challenges with the URL streaming feature. So if you guys want to try out AirFlick and share your experience if worked or not, please feel free to post on comments for the rest of us. We appreciate your feedback!