these are add-ons I install on every 'fresh' install. some because I like 'grey scale', a non-distracting, minimalist look some because I code; css, html, php & 'hack' UI xul, 18+ hours a day
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).
Download Flash and Video is a great download helper tool that lets you download Flash games and Flash videos (YouTube, Facebook, Dailymotion, Google Videos and more) with a single click.
The downloader is very easy to use.
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.
Never be annoyed by a Flash animation again! Blocks Flash so it won't get in your way, but if you want to see it, just click on...
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.
Smooth dark theme for Firefox
> BETA VERSION AVAILABLE HERE <
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.
Allows to customize or disable most of the shortcuts offered by Firefox. This add-on does *not* allow to add new shortcuts, but it might help you discover new ones.
The greatest user script engine on the Internet (a fork of Greasemonkey).
DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.
Multi-Translator from Google, Bing and Pragma.
Translation tool for your Firefox and Thunderbird with a simple and friendly interface.
Checks the (whole) web page (and not the text inside edit box) for spelling mistakes and highlights it.