I've created a JavaScript tool called TraceyText. It basically creates web pages that can display the source code of a program and annotate each step with notes. This allows you to go through a run of a program step by step with explanations on the way. I created this to demo the small games I made in Python for my free Creative Commons book, Invent Your Own Games with Python ( available at http://pythonbook.coffeeghost.net ) I'll admit the tool needs more documentation and demos, but here's a demo just to see how it works: http://traceytext.sourceforge.net/dragondemo.html The website is here: http://traceytext.sourceforge.net/ -Al Sweigart