12 *BSD books (FreeBSD,OpenBSD,NetBSD)

Absolute BSD The Ultimate Guide to FreeBSD

Absolute OpenBSD UNIX For The Practical Paranoid

BSD hacks

creating a transparent OpenBSD firewall

Embedded FreeBSD Cookbook

FreeBSD Architecture Handbook

OpenBSD pf firewall guide

OReilly Mastering FreeBSD and OpenBSD Security (Mar 2005)

Oreilly-The Complete Freebsd-(Fourth Edition)

Sams-Teach Yourself FreeBSD in 24 Hours

The Design and Implementation of the FreeBSD Operating System

The NetBSD Guide