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).
The simplest YouTube Video Downloader for all YouTube Flash sites, period.
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.
ImTranslator provides access to the online translation powered by Google Translate, Microsoft, Babylon for 66 languages. It includes dictionary, text-to-speech, back translation.
Complete Video Tutorial: http://youtu.be/UwK6529XZIQ
This add-on is a downloader that lets you easily download videos and music from sites like Youtube, Facebook, Metacafe, Dailymotion, Break, VKontakte, DivShare and music for example from SoundCloud, Grooveshark and from many other sites...
LastPass, an award-winning password manager, saves your passwords and gives you secure access from every computer and mobile device.
The Web Developer extension adds various web developer tools to the browser.
FoxyProxy is an advanced proxy management tool that completely replaces Firefox's limited proxying capabilities. For a simpler tool and less advanced configuration options, please use FoxyProxy Basic.
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
The most lightweight and easiest translator. Translate between more than 50 languages with one click or a hot key. Translate from one word to a whole page.
The quickest way to find out if your computer is infected!
Bitdefender QuickScan is a very fast antivirus scanner, able to determine in a matter of seconds if a system is infected with malware.
More on http://quickscan.bitdefender.com/faq