The TinyCircuits TinyDuino is an Arduino compatible board in an ultra compact package. Just think of the possibilities of having the power of an Arduino Uno on a 20mm square board, and a stack of 6 boards is less than 25mm (1in) high! The TinyDuino basic kit has the essentials to get you going with the TinyDuino system. It includes the TinyDuino Processor board with battery holder (73-4751), the TinyShield USB & ICP board (73-4752), one TinyShield Proto 1 board (73-4753), a 3 board mounting kit (screws, nuts and standoffs) and instructions for getting started.
The TinyCircuits TinyDuino Processor board is basically equivalent to the Arduino Uno board, with the same processor and the same signals brought out to a shield connector. In fact, most Arduino sketches will work without any changes. This board has the processor and shield connector on one side and a coin cell battery holder on the other.
The TinyDuino is released with the Open Source Hardware logo and the Creative Commons Attribution-ShareAlike 3.0 License and can be incorporated into commercial designs.