Arduino UNO R3 Microcontroller Development Board - Arduino Compatible
Arduino is an open-source physical computing platform based on a simple i/o board and a development environment that implements the Processing/Wiring language. Arduino can be used to develop stand-alone interactive objects or can be connected to software on your computer (e.g. Flash, Processing). The open-source IDE can be downloaded for free (currently for Mac OS X, Windows, and Linux).