Apple - Open Source
The "open source" portions of Apple technologies, including Darwin, aka the core of Mac OS X.
High Performance Computing using Mac OS X
Collection of open source tools for scientific computation: binaries, source, documentation and instructions for installing Fortran, MPI, OpenMP, Cactus, Globus and similar packages.
Mac OS Open Source Software Directory
An index of code-accessable programs for the Macintosh. Rapidly growing and regularly updated.