Arduino ( Atmega 8 or ATmega 168 based open-source electronics prototyping platform )
http://www.arduino.cc/ Make Magazine features Arduino as one of the most popular prototyping/education platforms 2007!!
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.
Arduino can sense the environment by receiving input from a variety of sensors and can affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is programmed using the Arduino programming language (based on Wiring) and the Arduino development environment (based on Processing). Arduino projects can be stand-alone or they can communicate with software on running on a computer (e.g. Flash, Processing, MaxMSP).
The boards can be assembled by hand or purchased preassembled; the software can be downloaded for free.
Similar project in Cypress PSOC CY8C29466
http://gainer.cc/Gainer.cc is a wonderfully simple board based on the Cypress PSoC CY8C29466. What makes this board so great is the pre-loaded bootloader developed by the Japanese based consortium named Gainer. Gainer allows you to program in Flash, Max/MSP, and even Processing!