Martin Atkins built this great LED matrix clock using an Arduino Micro, a few bicolor LED matrix displays, display drivers, and a real time clock module Chronodot:

Finally found some time today to solder the parts onto my first OSH Park PCB. The primary motivation for this was to learn Eagle and try out OSH Park, so I wanted to make something with only components I’d already purchased, and that’s why it has a whole Arduino Micro attached to it even though a smaller board (or even just a lone microcontroller) would’ve been sufficient. I didn’t get the displays lined up quite right, so there’s a small gap between them that looks obvious in this photo but isn’t so bad if you’re further away and looking at it head-on. But my learning for next time is to watch out for the positioning of odd-sized components.