Add-ons

FlashGot Mass Downloader by Giorgio Maone

Download all the links, movies and audio clips of a page at the maximum speed with a single click, using the most popular, lightweight and reliable external download managers.

Spanish (Spain) Dictionary by tnarik, RickieES

Spanish/Spain Dictionary

Session Manager by Michael Kraft

Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.

Menu Wizard by Oleksandr

Customize menus : Helps removing, moving and renaming menus and menu items
Colorize important menu for ease of use! (use Style (CSS))
Change or disable any of used keyboard shortcuts
Support: Firefox, Thunderbird and SeaMonkey

British English Dictionary by Mark Tyndall

British English Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey by David Bartlett.

To enable, right-click in a multi-line text box, select "Languages", then "English / United Kingdom".

Disable Add-on Compatibility Checks by Kris Maglione

Reinstates the extensions.checkCompatibility preference without respect to the current application version.

Arabic spell-checking dictionary by Dan Kenigsberg

Arabic spell-checking dictionary for Firefox 3 and Thunderbird 3 from Ayaspell.

United States English Spellchecker by jooliaan

This dictionary is no longer maintained. Use this dictionary instead.

Google Images by Dr_Monkey99

Google Images Search

Collector's Note Pas une extension mais un moteur de recherche (search engine plugin) qui s'installe directement dans la barre d'adresse et il suffit alors d'un clic pour faire une recherche.

Wolfram|Alpha by phoque

Search the brand new Wolfram|Alpha computational search engine.

Forecastfox Weather by Ensolis

Get international weather forecasts from AccuWeather.com and display them in any toolbar or statusbar with this highly customizable and unobtrusive extension.

Collector's Note Indispensable car: La météo (même hors des Etats-Unis !!) visible d'un coup d'oeil dans la barre d'état, sans ralentissements!

about:addons-memory by Nils Maier

Adds an about:addons-memory page that details add-on memory usage

Google Maps Search by LTD

Google Maps Search

Latin Dictionary by Leszek Życzkowski

Latin dictionary

AutoPager by Wind Li

AutoPager automatically loads next pages when you reach the end of a page. It works on a ton of sites,Google,Yahoo..
It works well with most other add-ons adblock plus, WOT and most of the greasemonkey scripts.
You can also try AutoPagerLite.

Collector's Note Permet de gagner un temps fou en remplaçant les multiples pages d'une recherche par exemple dans laquelle on doit naviguer, par une seule page géante dans laquelle on peut scroller à l'infini si on veut.