Apple comes to the rescue with a KnowledgeBase posting that will give you all the details on what systems are capable of using FaceTime. As you may know, FaceTime HD is a new feature of the just released MacBook Pro line, and Apple has taken FaceTime for the rest of us out of beta and made it a US $0.99 app.
While the HD feature of FaceTime is built into the just-released laptops because of an updated higher resolution camera, it doesn't mean those with older equipment are out of the game. Apple says you need Snow Leopard 10.6
