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.
LastPass, an award-winning password manager, saves your passwords and gives you secure access from every computer and mobile device.
AutoPager automatically loads next pages when you reach the end of a page. It works on a ton of sites,Google,Yahoo..
It works well with most other add-ons adblock plus, WOT and most of the greasemonkey scripts.
You can also try AutoPagerLite.
URL Fixer fixes common typos in URLs entered in the address bar. It will fix errors like "google.con" or "youtube,com". You have the option of being asked to confirm corrections before they are applied.
LinkyMobile is a Firefox/Firefox Mobile Addon to converts text links into genuine, clickable links.
Adds "Show password" menu into the long-tap context menu on a password field.
It would become easy to edit and confirm the password for yourself.
Copy your profile to the sdcard for easy debugging.
Search selected text with various search engines from the long-tap context menu.
This add-on provides the way to quickly search the selected text with your favorite search engines.