PF Sense Book.

Michael Lucas wrote an interesting review of the PF Sense book.  I use PFSense for my corporate firewall and really like it.  I have it installed on two servers and set it up to fail over using CARP.  The best part is that it works.  I've been using FreeBSD for years and all of my servers are FreeBSD, so I feel comfortable using PFSense because it runs FreeBSD underneath.