WeatherBug
Note from Mozilla: This add-on has been discontinued. Try Forecastfox Weather instead.Get live, local weather conditions in Firefox with the WeatherBug extension.
KidZui
KidZui turns Firefox into fun, kid-safe browser and online playground for kids 3-12 with over a million kids games, YouTube videos, and websites.
Glue - Recommendations for Books/Movies/Music
GetGlue helps you find your next favorite movie, book, or music album. As you visit sites like Amazon, IMDB, and Wikipedia, GetGlue suggest things you'll like.
Destroy the Web
Turn any webpage into a shoot-em up video game.With a pulse pounding soundtrack and high scores for every web page, Destroy the Web is a fun way to take a little break during the day.
Shareaholic | share with Google, Facebook and more
Shareaholic is the easiest way to share interesting links using Facebook, Twitter, Google Mail, Reader, Bookmarks, Evernote, Bitly, StumbleUpon, and more... from one simple ALL-IN-ONE add-on. This is the ultimate tool for the link sharing addict!
Delicious Bookmarks
Delicious Bookmarks is the official Firefox add-on for Delicious, the world's leading social bookmarking service (formerly del.icio.us). It integrates your bookmarks and tags with Firefox and keeps them in sync for easy, convenient access.
InvisibleHand
Automatically get the lowest price when you shop online or search for flights. InvisibleHand shows a discreet notification when a better price is available on a product or flight you're shopping for. Covers over 580 retailers in the US, UK & Germany.
Yoono: Twitter Facebook LinkedIn YouTube GTalk AIM
All your social networks and instant messaging in one easy to use app - it's the #1 downloaded social networking add-on for Firefox. Get all your updates, update your status and share across Facebook, Twitter, LinkedIn, YouTube & more - all at once!
ReminderFox
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.