Greasemonkey Requires Restart
Flashblock Requires Restart
Never be annoyed by a Flash animation again! Blocks Flash so it won't get in your way, but if you want to see it, just click on...
With EPUBReader you can read ePub files just in Firefox. No additional software needed!
Garmin Communicator Requires Restart
The Garmin Communicator is an internet browser plugin that allows you to easily transfer data between websites and Garmin GPS devices.
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.
Hoxx VPN Proxy service to unblock blocked websites, hide your location and encrypt your connection. Completely free.
Add-ons Manager Context Menu Requires Restart
Add more items to Add-ons Manager context menu.
UnMHT allows you to view MHT (MHTML) web archive format files, and save complete web pages, including text and graphics, into a single MHT file in Firefox/SeaMonkey.
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 (legacy add-ons only).
Translate the whole entire page or just a selection using Google Translate.
Save as PDF Requires Restart
Lets you download web pages as PDF in one click.
Tampermonkey is the world's most popular userscript manager.
LeechBlock Requires Restart
LeechBlock is a simple productivity tool designed to block those time-wasting sites that can suck the life out of your working day. All you need to do is specify which sites to block and when to block them.
Low Quality Flash Requires Restart
Sets Flash objects to "Low Quality" to improve performance on slower platforms (i.e. older computers, netbooks, and Firefox Mobile).
Reinstates the extensions.checkCompatibility preference without respect to the current application version.
Selenium IDE Button Requires Restart
Just one simple toolbar button to open Selenium IDE. You need to have installed Selenium IDE: http://seleniumhq.org/projects/ide/
Copy Plain Text 2 Requires Restart
Copies text without formatting
Secure Login Requires Restart
Secure Login is an extension for Firefox integrated password manager.
For Firefox > 51, try my WebExtension implementation: https://addons.mozilla.org/en-US/firefox/addon/secure-login-webextension/