Tunneling protocols over SSH.
For example, checking your mail or browsing a website using
SSH. Explains local & remote port forwarding.
Upload code to run
remotely and tunnel back out. Complete annotated source
for a shell script that uses SSH in a somewhat unusual way
to upload & run code from a local machine remotely, and
then allow that code (or any other code) to connect back out
via the SSH connection. An example of cat | ssh
and SSH remote port forwarding. Hack!