Although a little buggy, Remote Control Pro, is a great free program I've been playing about with now that I have two machines networked. The free version being limited to remotely controlling just one machine. But then currently that's all I need.
So now, from either machine I can easily control the other as though I were sitting at the other machine. Okay so full screen video is a little jerky, and it didn't like a full screen 3D game I tested, but otherwise the results were pretty impressive.
As an added bonus, from the second computer, I now have a pseudo form of Internet sharing.