Physical Computing: Arduino
What is Arduino?
"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 environments."
(from the Arduino website)
Similar to Wiring, Arduino is both a hardware platform (the board) and a programming language/environment (to program the board).
NOTE: The Wiring and Arduino boards are both very popular in physical computing; use whichever of the two you get your hands on.
1. The Arduino board
NOTE: The Arduino board comes in a wide variety of sizes and technologies. For more details, check the Arduino website.
2. The Arduino IDE