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. http://www.onlamp.com/
Goal is to provide an easy way to install various open-source software products on a Darwin, Mac OS X, FreeBSD, or Linux system. http://darwinports.opendarwin.org/
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. http://handbrake.m0k.org/