PurplePaste

I've been using Firefox for over a year now (and through a number of name changes), and as many of my co-workers can attest, I'm a huge fan. And while many of the built in features that Firefox boasts are excellent (popup blocking, tabbed browsing, etc.), it's the plethora of extensions that really make this browser great.

Extensions are basically plugins -- they add some new functionality to the browser. There are great collections of Firefox extensions at: Mozilla Update and Extension Room

As a developer, I have a number of favorites, which include:

• ColorZilla - Extract color information and CSS class/id names by hovering over elements in a page.
• Web Developer toolbar - A very useful set of tools for web development work.
• Googlebar - Excellent set of tools for navigating Google search results and locating/highlighting keywords within a page.
• TabBrowser extensions - Organize tabs easily, drag and drop tabs, and set default behaviors for opening links into new or existing tabs. Lots of other options too.
• Live HTTP Headers - Great tool for examining HTTP requests/responses, very useful for developing web-enabled applications.
• AdBlock - Very useful extension. I'm all for ad-supported content, but when the ads overwhelm the content it becomes necessary to invoke the power of this little extension. It also blocks annoying Flash ads/animations, unless you click to enable them.
• MozCC - Resides in the status bar and displays Creative Commons licensing details when the content of a page contains an embedded Creative Commons license.

If it's not evident by my list, I make pretty frequent use of Firefox as a development tool, and not just a browser.