A new version of the Server Core step by step guide has been posted to TechNet, which includes the new Windows Server 2008 R2 commands (DISM.exe, new roles/features, etc):
I’ll blog more about the new commands and features in the coming months, with some new tips and tricks.
In addition to the new step by step guide for Server Core, there are also two job aids now available. These have some commonly used commands on a single sheet of paper that can be folded up and carried with you. A version for Windows Server 2008 and a version that includes some of the new Windows Server 2008 R2 commands are available at: