The extensions that I can't live without-default w/every FF installation
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).
Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager.
Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
Use the Evernote Web Clipper to save things you see on the web into your Evernote account.
Add useful extra features to Gmail, like hierarchical labels, an unread message icon on your browser tab, file attachment icons, and more.
View and manage downloads from a tidy statusbar - without the download window getting in the way of your web browsing.
Thanks Tekzilla for your awesome review! Click here to see their video: http://youtu.be/BUDqWrJ-Vao
This extension adds a new "FaviconizeTab" option to the context menu of the tab...
A compilation of some of the best Greasemonkey user scripts for YouTube in one interface.
Note from Mozilla: This add-on has been discontinued. Try PDF Viewer instead.
PDF plugin for Firefox 3 on Mac OS X. Displays PDF documents in the browser.
Adds collapsible header and sidebar, event title text wrap, colored weekend days, week numbers, and skins to Google Calendar.
Collections are groups of related add-ons that anyone can create and share.Explore Collections