This Scratch program, adapted from an earlier version by Prof. Zamanis, illustrates Bubble Sort algorithm in a step-by-step way. It also shows how BROADCAST can be used to accomplish some of the same modularity usually achieved by making new blocks (back in the day, Scratch didn't support user-defined blocks). It is intended to be used in conjunction with the sorting activities from csunplugged.org. (There are also examples of insertion sort and quicksort in Scratch provided on that site.)
Prof Zamanis, a colleague from Edmodo groups.