The Firebug Web Page Debugger, Firefox version
This extension brings a new Events panel that lists all of the event handlers
on the page grouped by event type. The panel also nicely integrates with other Firebug
panels and allows to quickly find out,
Firediff is a Firebug extension that tracks changes to a pages DOM and CSS.
List elements for each CSS selector, trial CSS selectors by typing them in.
Allows exporting data from the Net panel.
View and manage cookies in your browser
Log to your Firebug Console from PHP (FirePHP< 1.0)
extends Firebug's activation model with advanced features.
Test Driver for Firebug Itself, useful for extension authors