AMMDI is an open-notebook hypertext writing experiment, authored by Mike Travers aka mtraven. It's a work in progress and some parts are more polished than others. Comments welcome! More.
A big influence and so far the only one that isn't a person (John McCarthy invented the first version but it's grown quite beyond his original concept). I learned Lisp by hanging out at the MIT AI lab with some of the Symbolics founders, and have been using it as my main tool ever since. The Lisp Machine remains at the pinnacle of environments for programming as a design activity; I don't know why the state of the art hasn't advanced since then.