Power Twitter was designed to make the Twitter experience more full-bodied. The folks at Twitter are building a core competency in storing and delivering messages and understandably have been reluctant to get too bogged down in product design. This has allowed 3rd parties to build a great set of Twitter clients. Power Twitter is a little bit different because it interacts directly with the Twitter.com website. And because it is embedded in the browser, Firefox, you are able to do some pretty slick things!
Note
Firefox 1.5 – 3.0.*

TwitterFox is a Firefox extension that notifies you of your friends’ tweets on Twitter. This extension adds a tiny icon on the status bar which notifies you when your friends update their tweets. Also it has a small text input field to update your tweets.
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Firefox 2.0 – 3.1b2

FireStatus is a Firefox 3 extension that allows you to send status updates, notes and URL links simultaneously to multiple social networks and services, like Twitter, FaceBook and FriendFeed. It also displays updates from these services in notification popups, for a more “live” communication with your friends.
Note
Firefox 3.0 – 3.1b2

Twitbin is a firefox extension that allows you to keep up with all of your Twitter conversations right from your browser sidebar. Send messages, receive messages, share links, and more from Twitbin, the best twitter addon for firefox out there.
Note
Firefox 1.5 – 3.1b2

Freeware RS232 serial port monitor/sniffer which additionally can decode NMEA 0183, ABB RP570 & ABB SPA protocols. Use this software to fault trace your serial communication with the help of simple hardware. Many different connections are supported. The RP570 support enables you to see communication between a substation and the control center for example.