Social Source Commons

Sage is a lightweight RSS and Atom feed reader extension for Mozilla Firefox.

Add-in for Internet Explorer and Firefox, featuring pop-up blocker, spell-checking, and search engine.

Firefox Bookmark Synchronizer

Share your files privately and securely. Chat with your friends. Firefox addon.

The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools. It is designed for Firefox, Flock, Mozilla and Seamonkey, and will run on any platform that these browsers support including Windows, Mac and Linux.

RSS and Atom news reader/aggregator extension for Firefox and the web.

Firefox blogging tool add-on.

Firefox add-on that allows synchronization of bookmarks and history.

Password Manager and Web Form Filler which shares passwords between Internet Explorer and Firefox.

Firefox add-on that disables most everything on the net but html, css and images. Handy if your security conscious, or surfing in disreputable corners of the net. Does have the downside that most of the net needs the very things this plug-in turns off, including much of Salsa.

Firefox addon that eliminates banner advertisements.

Site to check SEO for a given webpage. Also a firefox addon.

This Firefox extension gathers the PageRank for the linking page, the anchor text used on the link, and checks whether the link is followed or not.

Enhance your blog while you write. Automatic images, tags, links and articles suggestions. Supports all major blogging platforms.

Firefox plugin from drop.io allowing you to upload files into a new "drop" by simply dragging the file icon or image from your computer onto the firefox browser window. Also supports dragging files from other websites onto the browser window.

Adds a menu and a toolbar with various web developer tools.

Get all CSS styles of selected text in Firefox / Thunderbird...

Firefox console extension that handles natural language commands.

SmarterFox helps you browse faster by speeding up common tasks such as searching Wikipedia, searching Google, visiting your bookmarks, and more. SmarterFox was written by Yongqian Li. It was formerly called "Smarter Wikipedia".

ArchiveFacebook is a Firefox add-on that downloads a user's photos, messages, activity stream, friends list, events and groups from Facebook

Add useful extra features to Gmail, like hierarchical labels, an unread message icon on your browser tab, file attachment icons, and more.

Auto-discovery button for editable websites - which typically are wikis.

HTTPS Everywhere is a Firefox extension produced as a collaboration between The Tor Project and the Electronic Frontier Foundation. It encrypts your communications with a number of major websites.

Many sites on the web offer some limited support for encryption over HTTPS, but make it difficult to use. For instance, they may default to unencrypted HTTP, or fill encrypted pages with links that go back to the unencrypted site. The HTTPS Everywhere extension fixes these problems by rewriting all requests to these sites to HTTPS.

IN DEVELOPMENT

A Firefox extension (add-on SDK) that tracks which sites you go to, what data you submit where and gives you a "quantified-self" view into your browsing habits.

Firefox OS is a Linux-based open-source operating system for smartphones and tablet computers and is set to be used on smart TVs.

Extension for Firefox for Android. Simple add-on for settings HTTP, SOCKS and SSL proxy settings. Works by default with Orbot: Tor on Android.