Currently, there are two modules:
science.stats, containing various implementations of statistical methods similar to those provided by R;
science.lin, for linear algebra.
I originally started this in order to add a reusable statistics module to D3.js, but now it's grown into a whole new project of its own!
The project structure and Makefile is based on that of D3, so a big thank you goes to Mike Bostock for this.