After an article on FARK.com a couple weeks ago I started looking closer at some Firefox Extensinos. You can find the main list of extensions over at MozDev.Org

ForecastFox - A great extension that puts 3 small icons on the status bar that gives you the current and future weather conditions for the city of your choice. I also find it has better accuracy than The Weather Network's WeatherEye.

Ebay Negs - A great little extension for anyone that uses Ebay. With the use of a quick context menu you can view all of a Buyer or Seller's negative feedbacks.

User Agent Toolbar Widget - Ever been to a site that tells you it can only be viewed with Internet Explorer? This solves that problem by allowing you to trick websites into thinking you are using a different browser.

TabBrowser Preferences - If you are using Firefox hopefully you are using Tabs, they are the greatest thing about Firefox. This extension allows you to set some preferences that you can't do in standard Firefox. The one I enjoy the most is that any link that would have opened in a new window now opens in a new tab.

Download Manager Extension - Haven't played with this one much, basically adds some nice functionality to the Download Manager, ability to re-download a file, easy resumes, etc...

FoxyTunes - This is possibly my favourite extension. I listen to music all day, and I surf the internet all day. This extension adds a small media player to the status bar that lets you control a whole host of media software (including Windows Media Player, and Winamp). The nice part is that it then hides your media player keeping it out of your way while you work.