The Web Developer extension adds various web developer tools to the browser.
Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
Personas are free, easy-to-install "skins" for Firefox. Personas Plus extends that built-in functionality to give you even more control and easier access to new, popular, and your own favorite Personas.
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
StumbleUpon is the easiest way to discover new and interesting photos, videos, web pages and more, recommended by a community of experts. Tell us what you are interested in and we recommend page after page of amazing stuff you’d never expect to see.
AutoPager automatically loads next pages when you reach the end of a page. It works on a ton of sites,Google,Yahoo..
It works well with most other add-ons adblock plus, WOT and most of the greasemonkey scripts.
You can also try AutoPagerLite.
Open IT Online allows you to open documents and images online without the need of any software to be installed. It supports Google Docs, Zoho, View Docs Online, Vuzit to edit/view documents and Snipshot, Pixlr, Sumo Paint, etc. to edit/view images.
Collections are groups of related add-ons that anyone can create and share.Explore Collections