Extensions by Weekly Downloads
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.
Speed Dial Requires Restart
Direct access to your most visited websites
NoRedirect Requires Restart
NoRedirect lets the user take control of HTTP redirects. It can be used to interdict an ISP's DNS search redirection hijacks, preview/screen "shortened" URLs (e.g., TinyURL), stop the annoying redirection of "smart" error pages, etc.
QuickNote Requires Restart
A simple note-taking extension.
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.
Torrent Tornado Requires Restart
Saved Password Editor Requires Restart
Adds the ability to create and edit entries in the password manager.
Mail Redirect Requires Restart
Allow to redirect (a.k.a. "remail") mail messages to other recipients.
DownThemAll! AntiContainer Requires Restart
Make the resources behind container pages easily downloadable by DownThemAll!
HttpFox Requires Restart
An HTTP analyzer addon for Firefox
Mozilla Archive Format, with MHT and Faithful Save Requires Restart
— Open web pages saved with Internet Explorer or other browsers (MHT)
— Save many tabs, video and audio reliably, in a single ZIP file (MAFF)
— Return to the original site you saved a page from, and more!
FireTray Requires Restart
A system tray extension for Linux and Windows, allowing to set up custom icon, hiding to tray instead of closing, display the number of unread messages in mailing applications, and other features ...
Simple Locale Switcher Requires Restart
An easier management of the user interface language
ReminderFox Requires Restart Featured
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.
Fire IE (FireIE, Enhanced IE) Requires Restart
Embeds Internet Explorer(IE) to use the powerful Firefox add-ons.
Not only an enhanced IE Tab, but also an enhanced Internet Explorer with Adblock Plus and FireGestures support.
Switch to the IE engine in one click and dismiss your IE.
Manages the Remote XUL whitelist to allow websites and local files to load XUL content. For versions compatible with Firefox 41 and lower, see All Versions page below.
Theme Font & Size Changer lets you change the global font size and font family used for the user interface in Firefox. Design your browser with your favorite font.
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
VKontakte.ru Downloader (music/videos/photos @ VK) Requires Restart
Download music, videos and photos from VK.com / vkontakte.ru. One-click download, natural filenames, displaying file size and bitrate for music, downloading HD video, downloading HQ photos. No spam, no usage of your account, no spyware.
Cookie Importer Requires Restart
Imports cookies from a textfile.
Reads Netscape standard cookies.txt files as exported by IE and others.
Very useful in combination with the Cookie Exporter add-on.