Arduino website

http://arduino.cc/

This is the arduino website where you can find very useful information on what an arduino can do, and how to use it. You can download the processing sotfware for free and browse and post comments and questions on the forum.

http://fritzing.org/ 

This is the fritzing website, which is a sotfware that helps you design your circuit, share information and learn about interactivity

Play

http://sodaplay.com/

Create and Play with wireframe creatures following Physical laws using Java Script.