Twidget

Twidget is a Dashboard widget that lets you send tweets without opening a browser.

Enter your Twitter username and password, the refresh frequency, and the type of content the widget will display.

In the What are you doing? field, you need to enter your new Twitter status message. You can see the previous one at the top, right next to the Status tag.

You have 140 characters to say whatever you want. You can also respond to tweets and mark them as favorites.