This is from a decade ago. While I'm sure the fundamentals haven't changed much, are there any more up-to-date versions?

* https://github.com/jlevy/the-art-of-command-line notes and tips on using the command-line, suitable for both beginners and experienced users

* https://github.com/tldr-pages/tldr collection of community-maintained help pages for command-line tools

* http://www.compciv.org/unix-tools/ examples for most common usecases

* https://devmanual.gentoo.org/tools-reference/bash/index.html Bash reference cheatsheet