TinyMatrix project
We've used this project a number of times. It' provides a fun project to teach soldering (dead bug style) as well as exposing kids to the programming aspect. We focus on the image creation and allow everyone to create a custom bitmap to load into the firmware. But to do so they have to take thier graph paper bit map and convert it first into binary and then into hexadecimal. We copy it into the code and then flash the chip on the spot. It's a great exposure for how computers handle information pictures to numbers and the different numbering systems ( binary, base10 , hex ). All in all a great project with a lot of shiny and teachable moments.
Based on the original project https://sites.google.com/site/tinymatrix/ by Tim Toner (tigeruppp/at/gmail.com)