I was browsing through the new titles that are on Safari and saw some planning guides around Windows Server 2008 (Active Directory Services, File Services, etc.). Of course, all of these are published as solution accelerators, because they are designed to assist IT professionals understand, plan, and implement solutions quicker (hence the term, solution accelerator). Some of these documents have been around for a while, but the Solution Accelerators section groups them all into one place. If you've not run across them before, you can find them here:
Microsoft TechNet : Microsoft Solution Accelerators
Among them are the Infrastructure Planning and Design Guides. There's guidance on Windows Server 2008, virtualization, and even IIS. But unfortunately, none out there yet for SQL Server. If you're looking on the security side, there are the OS security guides from Windows XP on up, including for Vista and 2008. Sorry, no Windows 7 yet.