Programmable circuit board with open-source IDE.

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or

Arduino refers to both the hardware (single boarded micro-controller) and the software (a minimized IDE based on the Processing IDE) which makes hardware prototyping simple and engaging for people with little or no programming experience.

Arduino is open-source, meaning that anyone can manufacture a compatible board and the official site offers detailed instructions. Similar projects include:

There are also similar pin compatible versions such as: