I'll focus on one I find particularly useful here: Hyperwords (https://addons.mozilla.org/en-US/firefox/addon/1941). Hyperwords adds a right-click menu to your mouse button so that by selecting text and right-clicking you can select from a dizzying array of commands. Search Google for the selected text, look up a dictionary definition, translate it one of 16 languages, copy it to your clipboard, even shop for it on Craigslist. The screenshot below shows how to search for YouTube videos of Pedro Martinez simply with a right-click and a couple of menu commands.

This is just one of the hundreds of add-ins available on Firefox. I urge you to follow the link at the top of the post and take a look. it will change the way you use your browser.
