UltraVNC: Remote Desktop Viewer

UltraVNC allows you to view others desktops, and is a free download for all Microsoft Windows operating systems. VNC (Virtual Network Computing) however is a protocol available for all operating systems. It is already installed on Ubuntu with the GNOME Desktop. It runs on ports 5800 and 5900 or ports of your choosing. You need to configure a secure password so that people will have a hard time hacking your connection.