Apple - Downloads - UNIX & Open Source: The UNIX & Open Source category of Mac OS X Downloads.
Calxalot Software: Open source freeware for Mac OS X.
DarwinPorts: Goal is to provide an easy way to install various open-source software products on a Darwin, Mac OS X, FreeBSD, or Linux system.
FinkCommander: A graphical user interface for Fink. (only for Jaguar, as of version 0.5.0)
HandBrake: A GPL'd multi-platform, multithreaded DVD to MPEG-4 ripper/converter. HandBrake was originally available on the BeOS, but now has been ported over to MacOS X and to GNU/Linux.
LAMP: An ambitious project to provide a POSIX environment on Mac OS.
Mac OS X Man Pages: Apple's collection of man pages available from the command line, but much easier to browse.
MacDevCenter: Mac development tutorials, opinion, and discussion from the O'Reilly Network.
ONLamp: O'Reilly's articles on LAMP: The Open Source Web Platform. Roughly defined as (but not limited to) MySQL used in conjunction with Linux, Apache, and either Perl, Python, or PHP.
Red Bird Island: Free software for the Mac of various genres.
The Fink Project: Unix software ported to Mac OS X, either as binaries, or from source.
The Mac GNU OS X Public Archive: Packages of all forms of Open Source Software including many Unix applications ported to or built for OS X.