Using Twitter, even casually, requires that you be available on the social network during much of the day. You can meet that requirement a little more easily by adding Twitter's widget to your home screen.
I like the simplicity of Twitter's widget: You can choose to show new Tweets from your feed, or Tweets that mention you. You can also write a Tweet directly from the widget, without having to open an app. And that's really all you need.
Twitter | Free