This list contains add-ons that supplement the core functionality of Firefox (for basic users, such as Grandma). Only two included add-ons (LastPass & X-Notifier) require any sort of setup.
The simplest YouTube Video Downloader for all YouTube Flash sites, period.
Adblock Plus Pop-up Addon extends the blocking functionality of Adblock Plus to those annoying pop-up windows that open on mouse clicks and other user actions.
Adblock Edge is a fork of the Adblock Plus version 2.1.2 extension for blocking advertisements on the web, without sponsored ads whitelist.
**This addon will be discontinued on June 2015**
LastPass, an award-winning password manager, saves your passwords and gives you secure access from every computer and mobile device.
Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.
Expand your email area by blocking and removing ads on the right hand side of the screen when using Gmail, Hotmail, Outlook.com and Yahoo Mail.
DuckDuckGo is the search engine that doesn't track you. We also have smarter answers and less clutter. This extension makes DuckDuckGo available in the address bar, search bar and right-click menu. Also adds a handy toolbar button with more features!
Notifier for gmail, yahoo, hotmail, aol and more webmails.
X-notifier(aka WebMail Notifier) checks your webmail accounts and notifies the number of unread emails...
Supports : gmail, yahoo, hotmail, POP3/IMAP, facebook, twitter and more
— 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!
Status bar widgets and progress indicators for Firefox 4+
This 15KB restartless add-on will add a "File" -> "Restart" menu item and a ctrl/cmd + alt + r hotkey to restart Firefox or Seamonkey.
Changes the Location Bar of Firefox into a Breadcrumb display with rich and interactive features.
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