Here is a list of Firefox extensions that I use:
DOM inspector – DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application.
Talkback – submit a ceash report to Mozilla.org
ForecastFox – Forecastfox is an extension that brings international weather from AccuWeather.com® to your Firefox web browser
SearchStatus – For every site you visit using, SearchStatus lets you view its Google PageRank, Google Category, Alexa popularity ranking, Alexa incoming links, Alexa related links and backward links from Google, Yahoo! and MSN.
FlashGot – meant to handle single and massive (“all” and “selection”) downloads with several external Download Managers.
Web Developer – The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools.
Opanda IExif – view Exif/GPS/IPTC information of digital image
ColorZilla – Advanced Eyedropper, ColorPicker, Page Zoomer and other colorful goodies
del.icio.us – http://del.icio.us/ keep share and discover all your favourite things
Live HTTP headers – view http headers of a page and while browsing
FireBug – web debugging evolved
Adsense notifier – Displays your adsense earnings on the statusbar
Extension developer – makes life easier for Firefox extension developers
Linky – It will let you open or download all or selected links, image links and even web addresses found in the text in separate or different tabs or windows
AAEN – Amazon Associates Earnings notifier. Displays your earnings from amazon associate program in the status bar (developped by me) 😉
Selenium IDE – Record, edit and play selenium tests
ILQ Extension toolbar – displays rank of the site measured in links
SpellBound – no more spelling mistakes ( + spell libraries for bg and en(us) )
Dictionary search – looks up selected word in an online dictionary
View Source Chart – Creates a colorfull chart of a webpage’s rendered source
ReminderFox – reminder and ToDo
+ some others which I am about to deinstall right now