I've read a bit about "The Pomodoro Technique" for maximizing productivity and training your brain to focus. Basically, it's 25 minutes of dedicated concentration to a project, then a 5 minute break. However, the kitchen timer might not be the best way to help my coworkers keep their own concentration (what with the tick-tick-ticking).
Quite pleasing, then, to find a handy timer to add to the toolbar on my Mac.
Pomodoro stays silently on your status bar. You can only start/stop it or make interruptions and resume. You can use the keyboard to manage your pomodoro effectively, without touching the mouse. Add a meaningful description, press Ok and pomodoro starts.
So fa, it's been quite effective for me, and even gives me a report on what I've been working on with stats for the workday. Their nudges to either try again or get back to work are customizable, so it stands out in my mind as a great example of lightweight-but-powerful user experience.