Is there a code visualization website for Racket programs (for novice WeScheme users) similar to what is available at Online Python Tutor? Needless to say, it would provide a great self-teaching or learning tool.
DrRacket provides a Stepper--it's one of the buttons in the toolbar--that shows the evaluation of programs written in Beginning and Intermediate student languages as a sequence of steps. Its interface is not as pretty as the page you point to--as the author of the Stepper, I can say this with confidence--but it's a visualization tool along the same lines as the one you describe.