Holiday cards that blink and beep have always fascinated us. This is our hackable DIY version made with an ATtiny13A and a few LEDs - push the button to play a short light show in the tree. We're sending these to friends and family this year. It's a handmade, hackable gift, and it was a ton of fun to build. This instructable explains our design, then you can grab the open source files and build your own.
You can buy a copy of our card at Seeed Studio. Assembled cards are ($15), and a kit for adventurous solderers is $12.
You can also see this article with the original formatting at DangerousPrototypes.com.