KDEtwitter is a Twitter widget in KDE 4.2 which allows you to quickly:
* Post messages directly from your desktop, without accessing your Twitter home page
* Get notified when you receive updates
You don’t have to configure anything other than your account and the password associated with it and you’re ready to tweet.
When you click Add Widgets (on top right corner of your desktop), a window labeled Add Widgets appears. It contains a list of all the plasmoids installed on your system, and each one has a description below its name.
And from this list you can select KDEtwitter and add to your desktop and after configuring the twitter username/password you should see something like ... from where you can receive & send messages.