Twitbin’s a cool addon for Firefox which allows you to follow you friend’s tweets and send your own tweets. It shows up as a sidebar on the browser. The latest version of Twitbin works on Firefox 3 RC1.

All you need to do is to install the addon, open the sidebar, login by clicking on the Home icon in the sidebar and you’re all set.

Link:
Twitbin Home page
Install Twitbin
Follow Twitbin on Twitter