The Pomodoro Technique is a time management method which harnesses the human attention span before being distracted, it uses a timer to break down work into intervals, traditionally 25 minutes in length, separated by short breaks (3-5 minutes in length).
Each interval is known as a pomodoro, after four pomodoros, take a longer break (15–30 minutes), reset your timer and repeat.
Several Promodo timers are available out there in both online and desktop multi platform variants, I use on my Windows box, which is highly configurable, with a tiny footprint and free, it can be had from: