Tomighty is a convenient, easy to use, eye candy desktop application that helps you organize and execute your tasks in the Pomodoro™ way.
It's open source. You can download the source code and modify it to fit your needs.
About the technique
The Pomodoro Technique® is a simple way to boost your productivity when performing mind-consuming tasks. It helps you keep yourself focused while reducing mental exhaustion. Read more about it at the official website.