Another useful program I use every week is GNU Screen. It provides virtual terminals at a single terminal. It's a bit like a window manager for a text terminal. If you are a command line junkie (and if you are at all serious about computing, you should be), this is an essential piece of software.
The main reason I use screen is for its persistence. If I am running a
long-running job on a remote machine (i.e. over ssh), like a large
apt-get upgrade, I'll put it in a screen session. This
way I can log out and, later, log in from anywhere and check on it. I
have even used it to persist nethack
sessions, though this isn't really necessary.
The only annoying part is that all of it's mappings are underneath C-a (ctrl+a), which is a very common Emacs/bash command, which I use a lot. To get the effect of C-a inside screen, you have to do it twice in a row because screen captures the first one.
If you don't already use it, try it out sometime.