P.S. I suggest also putting a 'broken since 2.1.5' on the 'packages' pfsense page. It will save many hours of avoidable frustration and avoidable ill will generation since presently the user is given to think the reason it won't start is 'down to' the user's poor configuration choices, even though no combination could work.
Fell of my chair again laughing, 2nd time this week while reading here. (was reluctant to jump on topic, might cost me some karma :D)
What are you drinking lately? (must get me some of that too ;))
Indeed. The old book (linked above) is somewhat outdated but it's still covers a great deal. Some of the specifics will have changed but there is a huge amount of general networking/firewall info in that book.
Anything that covers pf such as you referenced above will give you great insight into the underlying processes but won't be much help in using pfSense specifically.
Google sites doesn't like IE? ::) If you go to the site and just click the file it takes you to a 'download page' of some sort. I expect you were actually downloading the html for that instead.
I'll add a note to the docs.