The good folks over at Apple have released a nearly 250 page PDF detailing best practices, hardware security, the four token models in OSX (Belgium National Identification Card (BELPIC), Department of Defense Common Access Card (CAC), Japanese government PKI (JPKI), and the U.S. Federal Government Personal Identity Verification, aka FIPS-201(PIV)) and a bunch of other subjects.  The guide is targeted at more experienced users, primarily IT technicians that have experience with the command line.  Whether you have experience with the command line or not, its probably good to read it if you have a Mac.  Who knows, you might learn something in the process. (You will, so read it).

Here's a chapter listing:

Chapter 1, “Introduction to Mac OS X Security Architecture,” explains the infrastructure of Mac OS X. It also discusses the layers of security in Mac OS X.
Chapter 2, “Installing Mac OS X,” describes how to securely install Mac OS X. The chapter also discusses how to securely install software updates and explains permissions and how to repair them.
Chapter 3, “Protecting System Hardware,” explains how to physically protect your hardware from attacks. This chapter also tells you how to secure settings that affect users of the computer.
Chapter 4, “Securing Global System Settings,” describes how to secure global system settings such as firmware and Mac OS X startup. There is also information on setting up system logs to monitor system activity.
Chapter 5, “Securing Accounts,” describes the types of user accounts and how to securely configure an account. This includes securing the system administrator account, using Open Directory, and using strong authentication.
Chapter 6, “Securing System Preferences,” describes recommended settings to secure Mac OS X system preferences.
Chapter 7, “Securing Data and Using Encryption,” describes how to encrypt data and how to use Secure Erase to verify that old data is completely removed.
Chapter 8, “Securing System Swap and Hibernation Storage,” describes how to secure your system swap and hibernation space of sensitive information.
Chapter 9, “Avoiding Multiple Simultaneous Account Access,” describes how to avoid fast user switching and local account access to the computer.
Chapter 10, “Ensuring Data Integrity with Backups,” describes the Time Machine architecture and how to securely backup and restore your computer and data.
Chapter 11, “Information Assurance with Applications,” describes how to protect your data while using Apple applications.
Chapter 12, “Information Assurance with Services,” describes how to secure your computer services. It also describes how to protect the computer by securely configuring services.