Inside Mac OS X 10.5 (Leopard) there is a new feature called screen sharing. Basically the way it works is if another computer is connected to the local network with remote desktop (VNC) or screen sharing enabled it shows up in the Shared section of the Finder like this:

Clicking on “Share Screen” asks for a password and then you can remotely take control of the other computer.
Now it starts to get interesting. I enabled Remote Desktop on a Ubuntu 7.10 box and OSX saw it immediately. So basically it’s completely cross platform compatible. So I thought maybe I could use this application as a general purpose VNC client, and yes you can!
The “Screen Sharing” application is stored in file:///System/Library/CoreServices/.

So basically I dragged it into the Dock and now it’s there for me to connect to your box whenever I want. All it asks is for the host and password if needed so it doesn’t have any advanced features at all. But it works.