SSH is a fantastic tool for working on computers remotely. However, I've often run into the following problem: I'll be doing something in the terminal, like downloading a new release of Ubuntu, and been forced to shut down due to battery depletion on my laptop.
Fortunately, there's a utility that allows you to run a terminal as a separate process. You can detach from that terminal, disconnect from your remote machine, and re-connect when you feel like it.
Screen is a GNU/Linux program that allows you to run a terminal without the headache of staying logged in via SSH. I've used it to begin a download at school, detach from the session, drive home, and then reattach to see the progress. It's very handy for situations that require multiple tty's.
To use it, just type the following command into the terminal of the remote machine:
This will bring you to a new, separate tty. Begin your process, then hit Ctrl-A+D (that is, hit Ctrl-A, then D for detach). This will take you out of the screen tty, leaving it running as a separate process. You can reattach to a screen later by typing screen -r.