I divided this article in three sections – Web development, Social development related plugins and finally just overall handy plugins for better browsing.
Also I must remind you, you will not find already popular and well known extensions here, since the mayor community already are know such plugins like – GreaseMonkey, WebDeveloper or Firebug tools for example. Just scroll through the list, check screenshots and hopefully several of these plugins will be useful for your daily Firefox internet browsing.
Web Development Related Firefox Plugins
Creates a color palette for Photoshop, Paint Shop Pro, GIMP, Flash, Fireworks, Paint.NET, or OS X based on the current page. This plugin is great using together with ColorPicker, actually extends possibilities.
Check the validity of links on any web page, this plugin is good for web designers and actually bloggers too.
There’s also a tool-bar button that can be added for easier access to LinkChecker. Just right click on your tool-bar, choose “Customize” and look for the button with the underlined blue check.
Just a little bit faster and handier way how to check site cookies.
It adds a tab to the Page Info dialog box, which shows the cookies of the
current web-page. This is interesting for developers, privacy-conscious users and others.