SharePoint 2007 Protocols and Ports
In researching how to deploy MOSS into a customer's data centre, I needed to find out exactly what and how was being communicated between the various MOSS servers. Surprisingly, Microsoft.com is a bit light on details, although there is a reasonable "security hardening" document available on TechNet.
The winner for me was this post from Joel Oleson. It's short, to the point, and answers the obvious questions.