The collection I use @work and @home. I like shortcuts, fast browsing, small top bars and efficient development tools.
Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
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.
Collector's Note I use Stylish on a Firefox customisation purpsoe only. With Iconic Menubar + Icons-Only Menubar, I moved my Menubar elements on the Adress Bar.
LastPass, an award-winning password manager, saves your passwords and gives you secure access from every computer and mobile device.
Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.
Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager.
The Web Developer extension adds various web developer tools to the browser.
Collector's Note You can regroup the web developer toolbar icons with other firefox toolbar when right click/edit on toolbars. Thus you will have the useful icons without having one more toolbar.
Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...
IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox...
Adds zoom and rotation functionality for images...
Collector's Note This small add-on is very handy has you will easily zoom images in any web page.
Note from Mozilla: This add-on has been discontinued. Try Menu Icons Plus instead.
Adds icons to all menus along with some other features...
Useful tools for the nightly tester.
Collector's Note Most of Firefox add-ons are not updated to maxversion, even if they are compatible. For instance, all the add-ons I used with Firefox 3.0 work with Firefox 3.5. Thanks to this add-on, I got back all of them with a single click!
Jump-to-word buttons and highlighting for the search box content
A complete redesign of popular Google services, Google Redesigned changes the appearance of popular Google services.