The Logo programming language is an amazing teaching tool and a lot of fun.
It includes a graphical system called "Turtle Graphics" where you give instructions to a turtle, and the turtle moves around, drawing as she goes.
Logo has been reimplemented many times, for every platform. It was first invented (or discovered?) by Wally Feurzeig, Seymour Papert, and Cynthia Solomon in 1967, the same year as the Beatles released "Sgt Peppers".
The first implementation of Logo, called Ghost, was written in LISP on a PDP-1. The goal was to create a mathematical land where children could play with words and sentences
The work of Seymour Papert did much to popularize the language and spread the idea, particularly the book Mindstorms, subtitle: "Children, Computers, and Powerful Ideas" which is available online here (thanks to the generosity of Papert's family).