Configuring PF

[Pat Maddox]

I want to install a firewall on my system.  First of all, is PF the
one I should be using?  It seems to get the most recommendations.

I don't actually seem to have any problems configuring it - I just
have some problems testing the configuration.  I can ssh to the box,
and I can access port 80...but I'd like to be able to just scan it to
quickly see what's up.  When PF is disabled, I can nmap it in about 9
seconds.  When I turn it on, it takes over 3 minutes to do.  These
machines are on the same network, so the connection is obviously fast.

Are there any good, pretty simple guides on setting up PF?  I'm having
a tough time understanding what the rulesets all mean.