Buzzbird is a free, open source Twitter client that will allow you to manage multiple accounts on the micro-blogging service.
If you are used to a client like Echofon or TweetDeck, your first impression of Buzzbird might be that it looks a little basic. Don't let appearances deceive you, however, because behind the main interface are a host of options, including support for multiple accounts and a built-in URL shortener.
Buzzbird offers all the usual Twitter client options, like posting, retweeting, direct messaging and marking as favorites. It's very easy to view your tweets, and the program also displays profiles without having to open a web browser. With Buzzbird, you'll also be able to view mentions and direct messages.
Unfortunately, Buzzbird doesn't minimize to the system tray while you are not using it and this, combined with the slightly old-fashioned appearance, means that using the app can feel a little clunky.
Clunky feel aside, Buzzbird is a great new Twitter client.