Here are the FireFox add-ons that I use

NoScript

Essential security for your web browser! Allow active content to run only from sites you trust, and protect yourself against XSS and Clickjacking attacks.

Firebug

Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

CodeBurner for Firebug

CodeBurner is a Firefox add-on that integrates with Firebug, to extend it with reference material for HTML and CSS.

Firefinder for Firebug

Finds HTML elements matching chosen CSS selector(s) or XPath expression

CoLT

CoLT makes it easy to copy either a hyperlink’s text or both the link and the link’s text (in a format you specify). Two handy context-menu items make this possible, and don’t add clutter; the items are only visible when right-clicking a link! Using CoLT to make this list, right click on the link to the Add-On in the search page, press o (for “cOpy link text and location as”), press Enter (HTML is the default, plain text and BBCode are some of the other options).

ColorZilla

Advanced Eyedropper, ColorPicker, Page Zoomer and other colorful goodies…

Live HTTP Headers

View HTTP headers of a page while browsing.

TwitterBar

Post to Twitter from your address bar.

BetterPrivacy

Ever wondered why you are still tracked though you tried everything to prevent it?
BetterPrivacy is a safeguard which protects from usually not deletable LSO’s on Google, YouTube, Ebay…

Clipmarks

Clipmarks lets you clip and share specific parts of articles, blog posts or anything else you read on the web. With our newly integrated Amplify service, you can post clips directly to Twitter or Facebook – or share them on clipmarks.com and more.

Download Statusbar

View and manage downloads from a tidy statusbar – without the download window getting in the way of your web browsing.

Pixel Perfect

Pixel Perfect is a Firefox/Firebug extension that allows web developers and designers to easily overlay a web composition over top of the developed HTML.

CSS Usage

Just found this one, I’ve been wanting to clean out my CSS! Firebug extension to view which CSS rules are actually used.

FireFTP

FireFTP is a free, secure, cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers. (I use FileZilla instead, easier for multiple projects; but FireFTP runs inside Firefox.)

FlashGot

Download all the links, movies and audio clips of a page at the maximum speed with a single click, using the most popular, lightweight and reliable external download managers.

IE View Lite

This is a cut down version of IE View by Paul Roub, which is 47.4 KB. All the same UI and features are there. It has a right click menu item to open a page in IE and a list of sites to always open in IE. It can close tabs automatically and send.

iMacros for Firefox

Automate Firefox. Record and replay repetitious work. If you love the Firefox web browser, but are tired of repetitive tasks like visiting the same sites every days, filling out forms, and remembering passwords, then iMacros for Firefox is the solution you’ve been dreaming of! Whatever you do with Firefox, iMacros can automate it.

I have automated reading ClickBank data into a database form; and reading real estate listings, home values and rental prices, into a database.

Combined with MySQL PHP Generator – Free PHP MySQL Generator by SQL Maestro Group you have a relatively easy to use (compared to coding in PHP) data scraping to database system.

InFormEnter

InFormEnter adds a small, clickable icon next to every input field in a web form, from where you can select the item to be inserted – no typing required (but I press Insert, quicker). You can configure it to display your frequently used information such as name, email, address, library card number.

Minimap Sidebar

The Minimap Addon gives you a suite of built-in maps and mapping tools for your web browser. Drag and Drop addresses or address links you find on web pages to view their location in the Map Sidebar, or by manually adding locations.

Operator

Operator leverages microformats and other semantic data that are already available on many web pages to provide new ways to interact with web services.

Save Complete

Saves a webpage completely, providing a better alternative to the built-in save functionality of Firefox.

Screengrab

Screengrab! saves webpages as images…

It will capture what you can see in the window, the entire page, just a selection, a particular frame… basically it saves webpages as images – either to a file, or to the clipboard. It captures Flash too!

SenSEO

SenSEO is an extension checking the most important on-page-SEO-criteria and calculating a grade of how good your site fulfills these criteria.

Add-Ons I Sometimes Use

DOM Inspector

DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.