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).
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 User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox...
With gTranslate you can translate any text in a webpage just by selecting and right-clicking over it. The extension uses the Google translation services to translate the text.
Readability is a simple tool that makes reading on the Web more comfortable by removing the clutter around what you are reading.
Manages the Remote XUL whitelist to allow websites and local files to load XUL content.
Expands the context menu's 'Search for' item into a list of installed search engines, allowing you to choose the engine you want to use for each search.
Free Catalan (general version) spelling dictionary.
Collections are groups of related add-ons that anyone can create and share.Explore Collections