Bit-Shift.Net

ComputerWorld is running an article listing 20 must have extensions for the Firefox web browser. Extensions for Firefox are small add-on modules, written by the Firefox team or independent developers, that (usually) improve the behavior of Firefox.

The extensions from the article I already use are:

• GreaseMonkey -  Allows you to customize the way a webpage displays using small bits of JavaScript.  Hundreds of scripts, for a wide variety of poular sites, are already available at Userscripts.org. I recommend the HTTP-> HTTPS redirector.
• IE Tab - Once installed, it places a small icon in your status bar. Clicking this icon swaps out the rendering engine from Firefox's to Internet Explorer's.
• FireBug - Allows you to examine and tweak the HTML, CSS and JavaScript contained in a page, all on the fly. This is a great tool for any web developer.

One of the extensions I've come to love that is not listed in the article is TabMixPlus. This add-on enhances the tabbed browsing experience of Firefox with features like controlling tab focus, duplicating tabs and a full-featured session manager with crash recovery that can save and restore combinations of opened tabs and windows.

With features like these and the ability to add pretty much any feature you can dream of, it's no wonder that IE is feeling the heat from Firefox.