I love these white papers from "How Microsoft Does IT." Obviously these guys are very skilled and knowledgeable when it comes to deploying their own technology. The insight you get is invaluable and really comes in to play when designing your own installations.
From the web site:
Ever wondered how a large enterprise plans and implements design and architecture of its next generation of messaging system? View this content to find out how engineers from the Microsoft IT messaging team will uncover the details on how Exchange 2007 infrastructure was introduced and fully deployed in a 120,000+ mailbox production environment. Topics will include: messaging topology design, hardware planning for various Exchange server roles, Client Access Server and Mobility scenarios, Transport architecture, Mailbox server and storage designs, backup, restore and high availability strategies.