FreeNX is kind of like VNC, but encrypted and can supposedly work well over 56k modems. I’m playing with it now and it seems to work well. The sever for Linux is free and install details can be found here:

http://www.knoppix.net/forum/viewtopic.php?t=12900

Windows and Linux clients can be found here:

http://web01.nomachine.com/download.php

After trying giving it a shot, looks nice but the cursor lags behind when I use it across my cable modem connection. What do you all think of it?