Digital clocks are quite common project among embedded hobbyists. You can find many variations of them in the internet. Some of them are wearable watch size, other use dot matrix LED displays. But main idea is to display time digits in binary code form.
This one looks pretty interesting besides its nerdy look. Actually it uses a pretty standard digital time display format, but there is another great looking feature – it displays seconds with analog meter. So additionally with binary time counting, Arduino has also control an analog voltage meter with PWM signal that is proportional to second’s value. This small touch makes whole project really unique and cool.