With apologies to anyone, throughout human history, who has ever made a rhyme:
Cult of Apple, heed my call,
Yee are the brightest of them all.
Help me with this strange request,
Cheap and easy would be best..
PowerBook and G4, they must chat,
Across the Internet, and stat!
What application do I need,
To make this work, and end this screed?
DarrenBarefoot.com 
http://www.apple.com/remotedesktop/
What, you couldn’t put it in verse? Just kidding, thanks.
Why not use VNC as a fallback? It’s also cross-platform, for when you need to access your mac from a windows box.
You GUI people, always trying to overcomplicated. What’s wrong with ssh? Comes with the system :).
Heh. I am ssh-capable, but it’s not for me. It’s for somebody who is somewhat less technically-apt.
Not exactly aimed at single users, but this should do what you’re looking for….
http://www.apple.com/remotedesktop/
Also, consider that if you don’t need the mac to host the connecting computers (that is, the mac is the one doing the remote connecting inward), you may be able to just get away with the remote desktop connection client that comes with office 2004. Check in the Additional Tools folder for this baby, or just search for ‘remote desktop connection’ in Finder.