Arduino
An open hardware project initiated by Massimo Banzi (Italy), David Cuartielles (Spain), Dave Mellis (USA), Nick Zambetti (USA).

Arduino is an open hardware system for artists and designers. It is a simplified microprocessor that allows an easy development of interactive installations and electro-mechanical artifacts. In only a few months since its creation several centres as the RCA in London, ITP New York, IDI-Domus in Milan, K3 in Malmö, among other institutions have adopted it as an educational tool.

http://arduino.berlios.de/

Processing
An open project initiated by Ben Fry and Casey Reas (USA).

Processing is an open source programming language and environment for students, artists, designers, architects and researchers and hobbyists interested in images, animation and sound programming and production.

http://processing.org/

Pure Data
A free software project initiated by Miller Puckette (USA).

Pure Data (PD) is a programmable environment for the audio and video analysis, synthesis, processing using a wide range of multimedia means. By being programmable in a graphic environment developed with free & open code and a modular structure, it is an extremely versatile tool, aplyable on fields as diverse as musical creation, audiovisual and interactive installations, VJing or theatre performances.

In order to develop a standard curriculum for electronic media creation using the Pure-Data programming environment Ben Bogart, Alexandre Castonguay and Hans-Christoph Steiner (USA) are developing the Pure Data Documentation Project (PDDP)

http://www.puredata.org/

http://www.puredata.org/dev/pddp