HoneyGinger is a recent success story that simulates fluid dynamics. The repository has some videos demonstrating the libraries capabilities. I've asked the author and he is happy to see the project listed here.
I recommend it gets placed in the Scientific libraries section e.g.
HoneyGinger - a fluid dynamics simulation engine focused on interactivity and visualization
Exercisim is a website for learning programming. A collection of problem statements are implemented as unit tests in various languages. People learn by creating solutions to these tests with TDD and getting mentor feedback.
We have created a Pharo-Smalltalk language track for Exercism. The repository is here and the language track on Exercism is here.