Virtual Network Computing
[What does VNC stand for, where is the home implementation, etc.?]
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/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 ].