MonkeyFly integrates some really awesome features to twitter’s web interface. Users can create tweetdeck like columns, upload image directly to twitpic etc. MonkeyFly is available as userscript, Firefox add-on and Chrome extension.

Want to create your own Twitter client?

How can you follow those thousands of people on twitter?

Mixero is a powerful twitter client and can be a substitute for Tweetdeck.