Screen or GNU Screen is a terminal multiplexer. In other words, it means that you can start a screen session and then open any number of windows (virtual terminals). This does not contain all of screen’s commands and options, read GNU’s manual to see everything

rTorrent is a command-line torrent application. Here are some shortcut keys.

Here’s some hints on using sed.

Quick reference to ANSI color codes.

GnuPG is a complete and free implementation of the OpenPGP standard.

See the processes in your Unix machine.

mattgreen/watchexec runs commands whenever certain files change.