This add-on lets you print a webpage's area easily.
Make your browsing experience faster by avoiding wait time on DNS lookups
Get rid of legacy Flash based embedded YouTube videos and replace them with YouTube's HTML5 player. Works even if you have Flash on.
Support for replacing the player on YouTube site is in development.
Toolbar button that lets you disable and re-enable Flash with just one click.
Allows you to quickly switch to a different language (User Interface, Spell Checker Dictionary and Website content) in your Mozilla application.
Customizes the new tab page. Add more tiles. Add the launcher from Firefox start. Have a background image. Set new tile images and titles. See recently closed tabs. And more...
Tweak Network will speed up the loading of web pages and increase the maximum number of simultaneous downloads from a site.
'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!
Open Bookmarks/History/Homepage/URL/Search in new tabs, and more utilities for tabbed browsing, including Protect/Lock/Faviconize/Unload Tab, Reload Every, Select and manipulate multiple tabs simultaneously, Tab Stacking/Coloring, etc.
Adds an about:addons-memory page that details add-on memory usage
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.
This extension is for those TB3 users who want the multiple-columns view that TB2 allowed
Allows to customize or disable most of the shortcuts offered by Firefox. This add-on does *not* allow to add new shortcuts, but it might help you discover existing ones.