TwitterFox is a Firefox extension that notifies you of your friends' statuses of Twitter. (former name is TwitterNotifier)

This extension adds a tiny icon on the status bar that notifies you when your friends update their statuses. Also it has a small text input field to update your status.

Firefox extension to Twitter from the firefox sidebar. Has ads.

Send tweets from your Maxthon browser
-v1.x, v2.0 and also toolbar plug

"Allows you to post from your browsers addressbar. I guess this is a type of clone of the Firefox Twitter Search Plugin, there are however a few differences - mainly it is NOT fired off to twitter at the hit of the return/enter key and therefore not revealing all your browsing secrets"

“Post to Twitter” is a search plugin for Mozilla Firefox which allows you to quickly post statuses (or “tweets”) to your Twitter account from the Firefox search bar. It is not an extension — it is a Firefox Search Engine. This means you can activate and install it in about five seconds, and start using it straight away without having to restart Firefox."

Power Twitter is a plugin for the Firefox browser that "greatly enhances" Twitter. Share social media to Twitter too.