Scenarios and Solutions are basically whiteboard solutions that quickly depict key engineering decisions.  You can think of them as baselines for your own design.   We have a set of solutions that show the most common end-to-end ASP.NET 2.0 authentication and authorization patterns:
 
Intranet

• Windows Authentication to AD Groups
• Windows Authentication to SQL Roles
• Forms Authentication to AD Roles

Internet

• Forms Authentication to SQL Roles

The advantage of starting with these you get to quickly see what combinations have worked for many others.