open a terminal and:
ssh -XC to-a-Linux-server-You-Have-Access-To
then run a gui-program from the command prompt of the remote box, such
as firefox. The program has to be accessible to you. Try looking in
/usr/local/bin for programs related to the gui interface, such as
gnome or kde. After several minutes and a few error messages, you'll
see the gui of the program displayed on your local box as the
X-session is piped through the SSH connection. If you get a return
such as:
[1] Done firefox
then it failed to start the program. Try another.
If you're on a Windows box, you'll need to install xcygwin first:
http://x.cygwin.com/
After it's installed, start an X session from the command line:
startx
Then see above steps to open a connection to a server you have access
to. I've tested this on Polaris and was able to bring up the Solaris
desktop. Pretty cool!