i too use ssh for the encryption also to port and X forward.
usually i just forward a simple app or two over rather than an entire environment like kde or gnome since i tend to live at the CLI other than for email or webrowsing (reading/posting @ LQ
). i use the port forwards to rdesktop to a few XP/2003 systems. from broadband to broadband this works rather nicely, when i am on the road and connecting from my laptop via dialup it can be a bit sluggish but that is to be expected.
I would have to agree with Archite about the vnc since it is cross-platform capable.