Microsoft published new guide about planning and design infrastructure in Windows Server 2008.
Main subject are:

• System Center Operations Manager 2007
• System Center Virtual Machine Manager 2008
• Internet Information Services 7.0
• NAP
• Microsoft SoftGrid Application Virtualization
• Windows Deployment Services
• Windows Server 2008 Active Directory Domain Services
• Windows Server 2008 Terminal Services
• Windows Server Virtualization: Hyper-V and Virtual Server 2005 R2 SP1

For Windows Server 2003 I recommend to read ??oWindows Server System Reference Architecture” guide.

Planning and Design Infrastructure
Windows Server System Reference Architecture