Learning Snort.

[phunked up! <phunkodelic () gmail com>]

Anybody have any good info on learing it?  I have installed
Snort/MySQL/PHP/Centos/Base and have it up and running.  I would like
a better understanding of how it works.  I have downloaded and read
the snort user guide.  I would prefer FREE as I don't want to add
another book to my collection.  Any help much appreciated.