The Web Developer extension adds various web developer tools to the browser.
A customizable mouse gestures extension which enables to execute various commands and user scripts with six types of gestures.
CodeBurner is a Firefox add-on that integrates with Firebug, to extend it with reference material for HTML and CSS.
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