dahmooser (with me) has released an excellent set of flowcharts that easily explain how Mac OS X, and also Mac OSx86 work. These flowcharts explain everything, from how it boots, what parts the kernel and the kexts come into, what is layered on top of the Darwin core to make OS X what it is, and everything. For a beginner looking into learning the basics of OSx86 and OS X on the technical side, these charts will help a ton.
A ZIP containing the flowcharts in PDF and the original MS Visio project file (if you want to make changes) can be downloaded here.
