With all the applications that are running on our macs it can be increasingly difficult to stay focused when you have some serious work to do. Most of the time I have multiple apps opened up with windows everywhere. I'm constantly switching from email, to safari, to twitter, to itunes, to text editors, to twitter....then to twitter again.
When play time is over and I have work or studying to do, there is a free app that helps me keep my focus on a single application.