Primitives for Bayesian MCMC inference
a Salesforce.com open source project
Pomagma — A deductive database for extensional λ-calculus
Kazoo — Experiments in psychoacoustics and musical instruments
The Rational Keyboard — A browser app experiment in just intonation
Johann — A toolset for statistical analysis of equations in combinatory algebras
Jenn3D — A toy for visualizing 4D Coxeter polytopes via stereographic projection to 3D
...more on github...
The Rational Keyboard is an HTML5 web app demonstrating a consonance model in just intonation. It's kind of like a piano with infinitely many keys (one for each rational number) that move around and resize based on what sounds good.