Build Your Own Tiny, Modular Arduino Inside a Tic Tac Box
The great thing about Arduinos is that they come in all shapes and sizes. You can also make one for yourself. Instructables user MakersBox did just that, with a tiny, modular Arduino-compatible board that can fit inside a Tic Tac box. 
The build uses a handful of parts, including an ATtiny capable of running the Arduino IDE. Once you get everything, you can simply snap the pieces together and stuff it inside a Tic-Tac box. What you do with it from there is entirely up to you. If youre not a fan of hunting down parts, you can also just order a kit with everything you need from Tindie.
Tacuino: a low-cost, modular, Arduino-compatible educational platform | Instructables

courtesy of lifehacker.com