•FireFTP – Looking for an FTP client you can reach from inside of Firefox?  FireFTP is a free, secure, cross platform FTP client built into and for Firefox.

•Picnik – Get quick access to your own online image editor with.  It adds a menu option to import images right into the Picnik online image editor.

•Stylish –often considered for web site tweakers, however it can also be used to add or remove CSS and design elements on the fly, without even having to login to your web site.

•User Agent Switcher – Another good one to have for cross browser testing.  It adds a menu to the toolbar so you can quickly change the user agent of the browser.

•FireShot – Take a screenshot and also add notes to it.  If you want to highlight key features of a design to a client, there is no better Firefox add-on.

•SeoQuake – Aimed at the search engine optimization crowd, this extension helps webmasters deal with the promotion of their domains.

Firebug’s CSS tabs tell you all you need to know about the styles in your web pages. If you don’t care for what it’s telling you, you can make changes and see them take effect on the spot. When your CSS boxes aren’t lining up correctly you certainly want to know why. Let Firebug be your eyes and it will measure and highlight all the offsets, margins, borders, padding, and sizes for you. Your pages are taking way to long to load, but why? Did you write too much JavaScript? Did you forget to compress your images?  Firebug breaks it all down for you file-by-file. When things aren’t going right, Firebug lets you know immediately and gives you detailed and useful information about errors in JavaScript, CSS, and XML.