Resources and Examples for Modeling Application Security Groups

I am searching for some resources and documentation on modeling security groups for a web application, but seem to be coming up rather dry.

I am interested in creating a visio-like diagram that displays all security groups in an application, what user roles those groups pertain to, and how to incorporate real world users into those roles.

Basically, I want to visualize the security architecture of a web application.

Maybe someone will have better luck then I Googling?

Thanks!