Need to know more statistics about the webpage you are viewing? Check out the extension Tab Data (+Memory usage). It provides the user with tab related stats and memory usage.
User-Agent Switcher can quickly and easily changes your browser’s user-agent. There are 25 popular user-agent strings to choose from too.
There are some powerful tweaking options in the “About” pages hidden deep within Firefox. Now, unless you have these memorized – they can sometimes be a little hard to remember. This is a very simple Firefox add-on consisting in a button which shows a list of all the “about” pages (including some other add-ons’ “about”).
Enjoy using Google’s homepage as your browser start page? It is easy and to the point with less mess or problems around it. What if though, you could add a few extra links to the webpage to help you jump to other links or services that Google provides? That is what the add-on, Easy Google Links, adds to the browser.
Plucki is a Firefox extension for users who want to remove all images from their Internet experience.
Mouse gestures for SeaMonkey & Firefox: navigate & execute commands using mouse gestures (with single mouse button) and rocker gestures (by pressing 2 mouse buttons). Also: scroll wheel navigation, page scrolling, tab scrolling.
Firefox Interest Dashboard provides a colorful and interactive view of your interests based on your browsing history.
Need Internet Explorer? Fire-IE is another ietab-like extension. It embeds the IE engine to handle IE-only websites. You could change the browser engine from Firefox to IE by a simple click.
A simple and super lightweight add-on for selecting any color from web pages.
Want to stay away from re-posting something on Reddit? The Reddit Submission Finder will crawl through Reddit and will make sure that your post has not been posted before by somebody else.