To extend his bit on "screen", not only can you detach and reattach to screen sessions, you can also do things like lock the terminal (ctrl-a ctrl-x), and have multiple terminals in one screen session (ctrl-a ctrl-c to create new ones). Screen is really sweet stuff, especially for when you're ssh'ing to a remote box.
Also, here's some configs I picked up from a mailing list a while back that puts a nice clock and listing of active screen terminals at the bottom. Pretty colors, too
It'll also make F7 and F8 be "back and forth" buttons for going through terminals.
Just put it in your .screenrc file in your home directory.