I have MAC OS X 10.6.8 (up-to-date). How can I get screen mirroring to my Apple TV to work? The icon does not appear at top status bar..

Welcome to the Apple Support Communities

See > http://support.apple.com/kb/HT5404 AirPlay Mirroring is compatible with Mid 2011 and newer MacBooks Air, and OS X Mountain Lion.

As you have Mac OS X Snow Leopard, you haven't got a compatible MacBook Air, so you can't use AirPlay Mirroring. However, you can use a third-party app as AirParrot to mirror the MacBook onto your Apple TV > http://www.airparrot.com

Of course. Check that you can use OS X Mountain Lion > http://www.apple.com/osx/specs However, this won't allow you to use AirPlay Mirroring, because your MacBook Air isn't compatible

is there other app like airparrot? that are free 🙂