At the command prompt type:
ssh -L [local port]:127.0.0.1:[remote port] [user]@[remote.host]

Example: ssh -L 5900:127.0.0.1:5900 modus@70.255.0.100

Next, simply point your VNC client to 127.0.0.1:5900

The -g switch on the ssh command will allow other machines to log in remotely through your machine.

-m