is a small menubar application that helps you concentrate. When you're working on a document, and don't want to be distracted, turn on Isolator. It will cover up your desktop and all the icons on it, as well as the windows of all your other applications, so you can concentrate on the task in hand.
Isolator is similar to, but not the same as Think and Backdrop. The difference is that it works exactly how I want it to. Maybe you'll like it too.