Always Up-to-Date Power User’s Guide to Firefox

 Now that Firefox is on a rapid release cycle, we're getting a new version of Firefox every three months—and each time, it becomes more tricked out than ever with new customization options, shortcuts, and convenient features hidden away in its menus. Today, we're covering it all—from longtime shortcuts to hidden features from the latest version of Firefox. Even if you're already a Firefox fanboy, there's bound to be something in here you haven't noticed before... "
Source: Lifehacker
 The Always Up-to-Date Power User's Guide to Firefox