Alarm clocks are cheap and abundant, but they're pretty boring. If you want to make your own, Instructables user Paranoid Legend shows you how to build one with an Arduino.
The alarm clock is made using a Arduino Mini and a TFT screen. You can turn the alarm on and off by flipping the clock, it's charged through a micro USB port, and it even senses your presence and saves power when you're not around. You can find the guide to build this for yourself over on Instructables.
Chronobot: A clever alarm clock [Instructables]