Restyle the web with Stylish, a user styles manager. Stylish lets you easily install themes and skins for Google, Facebook, YouTube, Orkut, and many, many other sites. You can even customize Firefox and other programs themselves.
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
The Web Developer extension adds various web developer tools to the browser.
View HTTP headers of a page and while browsing.
Control what gets sent as the HTTP Referer on a per-site basis.
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.
Secure Login is an extension for Firefox integrated password manager.
A Statusbar with speed, percentage, time and loaded size (similar to Opera's one)
Useful tools for the nightly tester.
Collections are groups of related add-ons that anyone can create and share.Explore Collections