September 7th, 2013
explainshell.com lets you view all the documentation for Unix/Linux command line arguments in one go, without needing to go near a manpage. Nifty.
Try ssh(1) -i keyfile -f -N -L 1234:www.google.com:80 host to get an idea of how this works in practice.
June 8th, 2009
One for the geeks: crontab2english is a simple Perl program that lists the contents of your crontab in something approaching plain English.
If only someone would produce a routine to pull the same trick with launchd's .plists. Lingon is fine as far as it goes, but it focuses on editing individual .plists and doesn't provide an overview of the characteristics of multiple .plists at a glance in the way crontab2english – or plain old crontab -l – does.