Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.
SQLite Manager Requires Restart
Manage any SQLite database on your computer.
ImportExportTools Requires Restart
Adds some tools to import and export folders and messages
If you are the kind of person who likes to have total control over every aspect of your downloads, "Download Status Bar" is the add-on you are looking for.
Provider for Google Calendar Requires Restart
Allows bidirectional access to Google Calendar
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
MinimizeToTray revived Requires Restart
Minimizes windows into the system tray.
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.
Add-ons Manager Context Menu Requires Restart
Add more items to Add-ons Manager context menu.
Font Finder Requires Restart
FontFinder is created for designers, developers and typographers. It allows a user to analyze the font information of any element on a page, copy any piece(s) of that information to the clipboard, and perform inline replacements to test new layouts.
'Classic Toolbar Buttons' add-on restores old toolbar button ui (known from Fx 4-7s small view, Fx 4-12s large view & Tb 5-14) for current Firefox, Thunderbird and Seamonkey versions on Windows.
Beta builds on versions page!
Diagnostics tool for Adblock Plus, provides some insight into internal processes of Adblock Plus.
Restart Requires Restart
"Restart" menu and button, with configurable shortcut key.
Adds toolbar buttons to the customize toolbar window in several programs including Firefox, Thunderbird and SeaMonkey. Some of the buttons make commonly preformed actions quicker, others add new functionality.
FoxClocks shows times around the world - or just your local time - at the bottom of your browser. It deals with daylight saving time so you don't have to.
ProfileSwitcher Requires Restart
It adds some options to launch easily other profiles and the Profile Manager.
Copy Plain Text 2 Requires Restart
Copies text without formatting
Google Calendar Tab Requires Restart
Adds the Google Calendar web interface as a new tab directly into Thunderbird. Creating and viewing events works just as it would in a browser like Firefox