He has a very interesting course at the Universidad de Buenos Aires about Mathematic Objects in Squeak. Soon there will be a site dedicated to this project. If this page is not updated, and you want some information about this, you can ask Leandro himself.
He's also a very active and enthusiastic member of SUGAR, and has made several SugarMiniatures which you can try.
You can find more information about the project in MathMorphs