VNC2Me site contains a few projects that allow support of remote users via screen or desktop sharing:
This Application utilises an SSH server connection to secure all communications between Viewer & Server.
It is used by many people who have existing SSH servers, and want a simply remote screen solution without the need to setup port forwarding.
This Application establishes a direct connection between the Viewer and Server. This speeds up the screen refreshes, but relies on port forwarding (if used behind a NAT router). The GUI is highly customisable, and allows for many different senarious (including manual entry of a viewer address).
Both Applications utilise UVNC in a reverse connection, thus eliminating the need for port forwarding on the VNC server, and making the VNC connection ALOT more secure.