Helpful Firefox Addon Software

OK, so I'm a newbie at all this stuff, but learning a ton!

I've just learned over the last week the power of Firefox browser software addons like Scribefire and Firebug. Being totally naive about this stuff as a newbie, I didn't even know these kinds of things existed. Nor did I know how easy it was to download and start using them!

I was wondering if you guys could put together a list of easy Firefox addon software that is really helpful when it comes to web design, blogging, etc. This would be a great post for any newbies to read if you did so!