http://scratch.mit.edu/
Scratch is a new programming language that makes it easy to create your own interactive stories, animations, games, music, and art using drag and drop -- and share your creations on the web.
Scratch is designed to help us develop 21st century learning skills. As we create and share Scratch projects, people learn important mathematical and computational ideas, while also learning to think creatively, reason systematically, and work collaboratively.
Scratch is available free of charge from
http://info.scratch.mit.edu/Scratch_1.4_Download
There is also a reference guide to help you at
http://info.scratch.mit.edu/Support/Reference_Guide_1.4
Just a side note to say that you have to have java installed to view this website porperly