tmux is a terminal multiplexer
What is a terminal multiplexer? It lets you switch easily between several programs in one terminal, detach them (they keep running in the background) and reattach them to a different terminal. And do a lot more. See the manual.
Download tmux %%RELEASE%% (changelog) or get the development version. tmux is hosted on SourceForge and needs libevent and ncurses.
For support contact the tmux-users@lists.sf.net mailing list or IRC channel #tmux on freenode.
There are some programs to use with tmux on GitHub and a book on tmux.