Scratch
A free application developed by MIT. By snapping together graphic programming blocks Tinkers can learn to solve problems, design projects and express themselves creatively on the computer.
Makey-Makey
Works like a keyboard and mouse and makes computer programs come to life!
Arduino
These circuit boards can be as simple or as complex as you can imagine! There are many kits to make fun projects with and the Arduino is compatible with scratch http://s4a.cat.