CheatSheet is lets you view available keyboard shortcuts in your current application. Just hold the ⌘-Key a bit longer to get a list of all active short cuts of the current application. It's as simple as that.
Shortcuts.design is a small website that lists every shortcut a designer ever wants to know, all designapps in one place and in a simple and clear way. It's very usefull for beginning designers to quickly charge their workflow, when you switched to a new designtool or when you just want a reference for repeating actions!
Pretzel is Mac desktop app that shows and find keyboard shortcuts based on your current app.
Power Menu is a highly configurable Finder extension that adds powerful actions to the right click menu and toolbar within Finder - this makes it quick and easy to do things such as move and copy files, convert images, create new documents and much more. The app comes bundled with preset actions and supports custom shell scripts.
Macro is a Chrome extension that makes users more productive on the web through keyboard shortcuts.
Macro offers powerful website-specific shortcuts and instant keyboard shortcut discovery across many websites. Think Reddit Enhancement Suite for the web. Learning one website's shortcuts means you won’t have to learn it again for a new website.