Celebrate Freedom With Firefox Extensions
ScribeFire

Get this, you can post to your blog from inside your browser. Oh wait, that's nothing new. Wouldn't it be cool if you could post to your blog when you were actually looking at another web page, using a client that runs on your desktop? Hrmm, OK, so ScribeFire doesn't sound as cool as it actually is when you're using it. With drag-n-drop photo posting and a host of handy features, it's what I use to update my (virtually never updated) blog.
Tab Catalog

Tab Catalog replicates one of the IE 7 features that I really dig. It shows thumbnails of all my open tabs. I do miss the old Reveal extension (which isn't compatible with Firefox 2), but Tab Catalog is a decent alternative.
The Coop

The Coop adds a sidebar to Firefox with all of your Facebook friends on it. This is an early proof-of-concept level prototype, but it's still useful. When you want to share something with a pal, just drag and drop it onto their picture and The Coop automatically sends them a Facebook message with a thumbnail and a relevant description. I have a lot of hope that this add-on will eventually come to fill the void left since development on Flock stalled.
TinyURL Creator
TinyURL is awesome, you put in a Amazon-length product URL, and it comes back with something that will easily fit on one line of an email. TinyURL Creator makes creating TinyURLs even easier. Just right-click a link and select Create TinyURL for this link, then the extension will contact the TinyURL server, request a new short URL, and copy the new URL to your clipboard. It doesn't get easier than that.
That's it! Please post your favorite Firefox Addons in the comments! I'd love to try them out.