Add-ons

Session Manager by Michael Kraft

Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.

UnMHT by arai_a

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.

Mozilla Archive Format, with MHT and Faithful Save by Christopher Ottley, Paolo Amadini

— 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!

Bluhell Firewall by Diego Casorran

Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.

Toolbar Buttons by Button Guy

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.

AutoCopy by Autocopy, Michael Lidman

Select text and it's automatically copied to the clipboard. Also pastes on middle click.

Private Tab by Infocatcher

Adds private tabs.

Right Links by Infocatcher

This extension allows to open links in new tabs with right-click directly and using “long” left-click.
This is very useful for touchpads on notebooks and for mice without middle button.

QuickDrag by Stevie Smith

Extends the function of the drag-and-drop mouse gesture so that it can be used to load URLs, do a web search of selected text on a page, or save an image on a page. The successor to Super DragAndGo.

Tabs Menu by Mikel Ward

Adds a Tabs menu to the main menu that lets you easily change between tabs.

Tom and Jerry by CP by Crazy Psychiatrist®

Textur - Abstraktes Gruen by Pixelfreak27