Apple just announced Facetime for mac which is in beta form. So there will only be iPod touch 4G to iPhone 4 to OS X-based devices supported.
It is not integrated into iChat it is separate app called “FaceTime”.This app use user address book and user can call friends and family.It is releasing today in beta form.

The features look pretty basic. You just click on a contact and it instantly makes a FaceTime call. Once you’re on the phone with them, a simple video window shows them in either landscape or portrait mode, depending on how they’re orienting their device.Samuel Axon-Mashable
If you dont know about this app you can read my article here.
Update:
Requires 10.6.4 Snow Leopard or later to work.
Download it from Apple site here.




