Greatest Firefox Extensions
Below is a list of my MUST HAVE Firefox extensions. These are not all of the Firefox extensions that I have installed, this is a list of extensions I feel everyone should have. Let me know if there is a truly great extension that I don't have listed but should.

Mouse Gestures - This is a must have! Makes life so much easier.  You will wonder how you lived without it after using it for a while.  I can't believe how much quicker you can navigate the web with this installed.

FoxyTunes - Great music player addin. Sits in the status bar and works with pretty much every media player.

Firebug - Must have for web development. Easy to use and unobtrusive. Very powerful for exploring the DOM, CSS, and JavaScript.

IE Tab - This one allows you to flip to the IE rendering engine inside Firefox. Very useful for testing web apps.  If you like me, you end up doing all your development work in Firefox and don't test in IE until the sites almost finished.  This extensions makes it very quick and easy to get an IE preview in a new Firefox tab.

del.icio.us - I don't know if you use del.icio.us or not, but if you do this is great for bookmarking. It's nice to have those bookmarks available wherever you may be.

Inform Enter - Great if you have to enter the same information into fields over and over. I use this when submitting sites to directories. It saves a ton of time.