Celebrate Freedom With Firefox Extensions
I can't deny it, the last twelve months have seen big changes for web browsers--Microsoft released IE7, Apple released Safari for Windows, and Opera is... well, doing Opera-tic stuff. But, frankly, I don't care. The kids over at Mozilla have earned my support and affection by making their browser extensible. By letting normal folks add more functionality to an already awesome browser, they've locked in my support. Sure, Safari might be a few fractions of a second faster loading pages, but I'm not going to give up the added functionality that Firefox's rich add-on ecology empowers me with.
I love to ask people who are hardcore web browsers what add-ons they've used to extend Firefox's functionality, but it occurs to me that I've never shared the stuff that I use every day. Some are useful, some save me a little time, and some are just plain cool. Enjoy!
ChromaTabs

This little add-on from the code wizards at Mozilla is about half user-interface design, and half flair. ChromaTabs changes the colors of different tabs based on the URL of the site. So, if you have multiple tabs open from a single site, you can immediately tell which sites are which based on the background color of the tab.
del.icio.us Bookmarks

It's always a special occasion when I find a software widget that improves the quality of my life. The first time I installed the del.icio.us Bookmarks plugin for Firefox was one such time. You see, instead of a clunky old flat file text file storing all my bookmarks, this plugin uses the del.icio.us service to sync my bookmarks with all my PCs, and share them with the world!
Firebug

I'm the web designer equivalent of a shade-tree mechanic, at least when it comes to web design. I know just enough to noodle around with a site's design until it looks like I want it to, but my best work is purely a result of trial and error. I make some changes to CSS and HTML to see what will happen, because I'm never 100% sure when I get started. Firebug lets me muck around with live website code from within my browser, without any risk to the site. It also includes tools to help reverse engineer site designs, letting you label and identify divs, spans, and other HTML constructs.