ShortcutFoo is a lean and simple Web app that lets you easily learn shortcut keys for Gmail and many other applications.

If you already have a shortcut to that command, it will appear in the adjacent Current keys: box; if there’s no command, that box will remain blank. To create a shortcut, press your keys choice.

Some shortcut keys are specific to your operating system, such as these keyboard shortcuts for Macs and Windows, and some are program-based, such as these keyboard shortcuts for Excel.