Mac: Keyboard shortcuts can save you lots of time and effort, but you have to know how to use them first. Eve is a Mac utility that can teach you every keyboard shortcut under the sun. When you perform a function or command with the mouse for which there's a corresponding keyboard shortcut, Eve will display the shortcut on the screen for you to learn and remember when to use it.
For example, if you click the "Go" menu in Finder and select "Connect to Server", Eve will pop up an alert box in the upper right corner of your screen with "Command K". It remembers which ones you've performed and only reminds you every now and then to avoid nagging you.
Eve currently supports shortcuts in Finder, Chrome, Safari and Apple's Mail app, but the developer is working on support for "almost all apps". For now, Eve is a great utility to try if you want to pick up keyboard shortcuts for any of the above core apps.