Add-ons

StartupMaster by htamas

Asks for the master password at startup (fixes multiple password prompt)

Disable Add-on Compatibility Checks by Kris Maglione

Reinstates the extensions.checkCompatibility preference without respect to the current application version.

Custom Buttons by Yan, cubegm, others

Gives a possibility to create custom toolbarbuttons...

Scriptish by Erik Vold, Nils Maier, others

The greatest user script engine on the Internet (a fork of Greasemonkey).

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.

No More Install Delay by trlkly

UPDATE: XPI delay has been removed in Firefox 40!

Disable the install delay in Firefox. New 2.0 version now includes GreaseMonkey scripts!

Unlike similar addons, this works on Firefox 4 and beyond.

ImageTweak: zoom/rotate images and videos! by Carlo Alberto Ferraris

A no-clutter image viewer for Firefox that allows you to zoom, rotate and display images/videos against a custom background. ImageTweak is a must-have addon for any photographer or photography-loving user.

InlineDisposition by Kai Liu

InlineDisposition changes the disposition of Content-Disposition response headers from attachment to inline; this prevents servers from forcing the browser to save a file and allows that file to be viewed in the browser, if the browser supports it.

Collector's Note Chrome样主题