The best security you can get in a web browser!
Allow active content to run only from sites you trust, and protect yourself against XSS and Clickjacking attacks.
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.
The Web Developer extension adds various web developer tools to the browser.
FireFTP is a free, secure, cross-platform FTP/SFTP client for Mozilla Firefox which provides easy and intuitive access to FTP/SFTP servers.
Check out my new project, FireSSH!
Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...
Adds ClickOnce support and the ability to report installed .NET versions to the web server.
When you find something on the web that you want to view later, put it in Pocket. It automatically syncs to your phone, tablet or computer so you can view it at any time, even without an internet connection.
Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.
IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox...
Tired of going to History -> Recently Closed Tabs just to undo a closed tab? Then this extension is for you!
This extension allows you to undo closed tabs via a toolbar button or the right-click context menu.
A productive way to organize, read and share the content of your favorite feeds, blogs and news sites. Feedly offers a seamless transition from Google Reader.