I spend a lot of time on Apple security, more for personal reasons than anything else. They are the tools I use every day, and where I send most of my friends and family to manage their digital lives, so my investment runs deeper than anything financial. I have been the Security Editor over at TidBITS since about the time I founded Securosis, but I am not the only security expert over there. Joe Kissell has himself written books on the topic, and plenty of articles (mostly at TidBITS and Macworld).
Joe is currently writing a Take Control book on Mac security. The Take Control series of books are my favorite hands-on instructional guides, and I have used a fair few myself (Take Control is distinct from TidBITS, but closely related and run by the same team).
The first two chapters are available free online at TidBITS. The rest of the chapters become available to TidBITS members as Joe writes them. These books run much deeper than the white papers and articles we post on Securosis. The book a soup-to-nuts hands-on guide for nearly everything you need to know to secure your own Mac.
Joe and I have talked about combining efforts for a Securosis/Take Control cross-branded version of the content if we can line up a licensee/sponsorship. If you are interested drop me a line.