Virtual Network Computing
VNC is a wonderful, truly cross-platform tool for using remote computers, similar to "PC Anywhere". It uses a standard IP connection, some versions can also use ssh for security. You can use the remote computer just like your own. It works fine with all kinds of X displays, all current Windows versions, ...
You can even use any Java-enabled Web browser as a client, because any VNC server will automatically send the necessary Java applet to the browser.
On Windows you become a second user of the graphical display - thus interfering with the person sitting at the computer, while the server version on Unix creates additional, invisible X displays which are only visible on the remote side. So on Unix computers several VNC servers can run at the same time without interfering with any other session on the same machine.
Note that the latest versions are now from RealVNC Ltd ( http://www.realvnc.com/ ), as AT&T has closed its Cambridge Labs. It can still be had from http://www.uk.research.att.com/archive/vnc/ .
RealVNC has nice enhancements, including automatic configuraton that tunes the encodings to suit the available bandwith.
See also http://xf4vnc.sourceforge.net/
CL published some of the first popular articles about VNC [L1 ].
Mac Cody's doing fascinating work binding Tcl to VNC in such combinations as TclRFB, described in "Create a VNC system with tclRFB" [L2 ].
stevel had good experiences with RealVNC.
DRH recommends tightVNC [L3 ].
Over on the Android page, someone mentioned that, using (client) VNC on a Unix machine, one could test GUI applications running on any platform with a VNC client.