like tabmixplus, lighter... haven't tried this yet

"makes a Firefox browser extension (XPI) from a given Greasemonkey user script."

"Places is a new system for storing bookmarks, history, and other information about pages. It is scheduled to go into Firefox 3."

Firefox extension that synchronize browsers of EVERYONE who installed the extension. Basically, it gets everyone on the same page. You can be passive (let other people browse for you) or active (change the collective current page).

"Monitors web pages for updates. Useful for websites that don't provide Atom or RSS feeds."

"enhances the Full Screen mode into a really full screen mode, hiding the remaining toolbars and statusbar and making them visible again when the mouse pointer hits an edge of the screen"

"allows you to post to twitter from the firefox addressbar"

(it's also the date format used in firefox bookmarks, so it can be useful to search a bookmark by date)

to be supported by firefox3

web web web

"Users will see their friends' faces, and by clicking on them will be able to get a list of that person's recently added Flickr photos, favourite YouTube videos, tagged websites, composed blog posts, updated Facebook status, etc."

colouring tabs by domains

"Minimeter vous permet de connaître l'état actuel du quota de votre connexion (ADSL ou cable) en l'affichant dans la barre d'état de Firefox."

the microformat extension

let you customize/replace/add favicons in your Firefox bookmarks

how to write extensions

"The Extension Wizard generates an extension skeleton to meet your needs. It is intended to save the time you would normally spend copying and pasting from your previous extensions or sample extensions."

The bird gazed down upon the unbelievers and cast fire
and thunder upon them. For the beast had been
reborn with its strength renewed, and the
followers of Mammon cowered in horror.

track your comments on various blogs & websites

isn't that a mixed rip-off of Forefox & Thunderbird logo ?

"Songbird is a Web player built from Firefox's browser engine. Songbird is open source, will run on Windows, Mac OS X and Linux and supports user contributed, cross-platform extensions."

MyStickies.com allows you to add post-it notes to any web page. To do so, you need to sign-up for an account and install the Firefox browser extension.

Chat live with other people who are looking at the same website as you!

excellent must-have firefox extensions

my favourite theme for firefox