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 Web Developer extension adds various web developer tools to the browser.
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
Help make Firefox better. The Add-on Compatibility Reporter enables you to report if the Firefox add-ons that you're using are working properly.
Combined with the ChromeToPhone application for Android, this extension allows to send urls, text and files from Firefox to your phone or tablet.
This addon was built to make debugging while using netbeans PHP easier.
The DeskSMS Android/iPhone application lets you send and receive text messages via Gmail, Gtalk, the web, Firefox and Chrome extensions from your own phone number!