Firefox is ace! The plugin architecture means that you can increase the functionality by adding extras.

All-In-One-Gestures

Control browser operations with your mouse https://addons.mozilla.org/en-US/firefox/addon/12

Out of all of them this makes navigation a dream. Imagine the following scenario: you are looking for something on the web and it is likely you will have to visit a lot of sites to find it. Typically, your hunt will start with a search on Google or some kind of specialist forum site. After you get your search results back you have 2 choices on navigation method.

1. Click the first link read what it says, find it's not what you want, click the back button then click the next link in the list, or
2. Mouse gesture down on each link on the page, which opens that page in a new tab, then starting with the first tab scan each page, closing it if it isn't relevant.

The choice is clear. One method uses twice the bandwidth, twice the processing power and takes 4 times longer; and the other method is what real men do (and by men I include computer women too).

British English Dictionary

Spell checker https://addons.mozilla.org/en-US/firefox/addon/3366

Everone shud spel propaly, evan the Amerikans.

Fetch Text URL

Text manipulator https://addons.mozilla.org/en-US/firefox/addon/518

This is a simple little utility that allows you to take a piece of plain text and launch it as a new web page. Not all webmail, forums or pages, spot URLs properly and don't automatically encase them in the appropriate <a hef= tags to create a link. The plugin lets you highlight a piece of text and launch it in a new browser or tab.

Firebug

Developer Tools https://addons.mozilla.org/en-US/firefox/addon/1843

No self-respecting web programmer should be with out this. It does everything from debugging Javascript, manipulating the DOM to breaking apart CSS and much more. If you've never seen it, check it out!

FireFTP

FTP Client https://addons.mozilla.org/en-US/firefox/addon/2200

Splits the screen in two to display local and remote files. Allows multiple file downloads.

Advanced URL Builder

Text manipulator https://addons.mozilla.org/en-US/firefox/addon/1399

Highlight some text and create a URL with it. Highlight a postcode from someone's "Contact Us" page and look it up on Google Maps.