GOR: Highlighting this one as we can add a lot of new content from this list.
This extensive collection of helpful lists, manuals, blogs, hacks, one-liners, cli/web tools and more can be useful in the daily life of a SysAdmin. For example: Can I use https://caniuse.com/#home provides up-to-date browser support tables for support of front-end web technologies. ShellCheck https://www.shellcheck.net/ finds bugs in your shell scripts. Shell & Utilities http://pubs.opengroup.org
