TweetDuck!

TweetDeck aims to evolve the existing functionality of Twitter by taking an abundance of information i.e twitter feeds, and breaking it down into more manageable bite sized pieces. From a poster's point of view, it supports shortening URLs by a couple of different services, posting and hosting images at different sites, and scheduling tweets to be posted even if you're offline.

Tweetdeckr is an open source TweetDeck replacement client.

Tweetium is first and foremost designed to be quick and reliable. All B-side Software apps have a special focus on fundamentals like performance and reliability, and Tweetium is a prime example of this. With its fast, modern UI, and multi-threaded sync and streaming architecture, you won't find a more fluid Twitter experience anywhere.