Seymour Papert invented the term constructionism to describe an educational philosophy that teaches children to do something rather than teaching them about something. Some of his early work involved teaching children to be mathemeticians rather than teaching them about mathematics in the traditional way.
This led to the LOGO language which is a form of LISP without the brackets. This language was developed in conjunction with a device called a turtle which was a small robot holding a pen which could be programmed to draw geometric shapes.
His work continued in a book called Mindstorms which led to him being invited to help the LEGO corporation develop the LEGO Mindstorms robotic kits.
He is in part of the OLPC project and is active in this wiki through the Learning Learning section.
There is a website with more information about him and his work here: http://www.papert.org