Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
Organize your schedule and life's important events in a calendar that's fully integrated with your Thunderbird email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.
Personas are free, easy-to-install "skins" for Firefox. Personas Plus extends that built-in functionality to give you even more control and easier access to new, popular, and your own favorite Personas.
Google and Zimbra contact sync for Thunderbird. (TB 24 and above NOT supported)
Displays the address books in a sidebar in Thunderbirds 3-pane-window and can be toggled with the F4 key or a toolbar button.
Visit my Contacts Sidebar site for recent versions and news.
The "Swiss army knife" of folders. Turn your favorites into tabs - open folders and subfolders, move mails without scrolling around or searching. powerful + easy.
See new mail at a glance after automatic filtering - supports quickFilters addon!
Display birthdays from the Thunderbird addressbooks as events in Lightning.
It adds a button that can be put in toolbars and that open the addressbook in a new tab
Collapse and expand quotes. Please see the extension homepage for...
Enter accents, diacritics, diaeresis, umlauts, ligatures etc. with keyboards of various countries (us,uk,ie,fr,it,ru,de,sv) - via easy to remember shortcuts or menu. Also supports all textboxes of the application (such as search, filters).
Toggles spelling dictionaries automatically or manually and displays the currently selected one in the status bar.
Now merged with Dictionary Switcher v1.3 for Firefox/SeaMonkey