trixbox

November 8th can be called the relaunch of development for the Asterisk/Drupal module. I worked with the Asterisk PBX as an application a few years ago. At the time I found these resources extremely helpful:

http://trixbox.org/
TrixBox is a GPL application that rolls Asterisk, a full Linux install, Apache, MySQL and PHP and a variety of Asterisk supporting applications such as Festival into a single ISO.
If you haven't touched Asterisk before and want a head start, put this onto an extra PC and you will be golden!