A lot of Linux command line tips and tricks.

A tool for generating RFC-like protocol header diagrams.

<blockquote>An open-source guide to help you write better command-line programs, taking traditional UNIX principles and updating them for the modern day.</blockquote>

ftp ipv4.cat
telnet ipv4.cat
ncat ipv4.cat
curl ipv4.cat
http://ipv4.cat

<blockquote>A short description and screenshot of some useful command line tools I use that aren't part of typical POSIX environment.</blockquote>