Scratch is a free educational tool developed by the Lifelong Kindergarten Group at the MIT Media Lab. It can be used to teach programming concepts, and served as my introduction to the world of computer science. I was an early user of the Scratch website, which launched in 2007 and allowed users to share and edit projects. As well as uploading my own code, I was given the opportunity to participate in a study run by the guys at MIT into how their website was being used.
Use of Scratch in the classroom is now a global phenomenon, and the tool has come a long way from its early days. My old projects can still be accessed here.