fish shell - The friendly interactive shell.
cheat - Cheat allows you to create and view interactive cheatsheets on the command-line.
zsh - The Z shell (Zsh) is a Unix shell that can be used as an interactive login shell and as a powerful command interpreter for shell scripting.
cheat.sh - The only cheat sheet you need Unified access to the best community driven documentation
PowerShell Plus - Learn how to learn and master PowerShell fast with an interactive learning center, a powerful IDE, pre-loaded scripts, and a PowerShell Editor… all for free.
explainshell - Match command-line arguments to their help.