TightVNC is an improved version of VNC, great free remote-desktop tool. The improvements include bandwidth-friendly "Tight" encoding, file transfers in the Windows version, enhanced GUI, many bugfixes, and more.
ARD is a remote administration tool for Unix/Linux & 95/98/ME/NT/2000 systems. Based on VNC technology , you can use ARD of the VNC to interact with a remote computer as though it's right next to you. ARD is great free remote-desktop tool.