Windows

I wish i knew of some good books...what is your organization structure/type?
check out technet downloads at www.microsoft.com
they have some interesting Active Directory Design docs guides, like:
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The Active Directory Branch Office Guide was created to help network managers, system integrators, and consultants involved in Active Directory branch office implementations. It describes all the tasks and decisions that must be completed to develop the Active Directory design for a large branch office deployment. It also describes how to develop a deployment plan and provides the step-by-step deployment procedures required to implement the design. While this guide is focused on branch office deployment, the issues and concepts discussed here will frequently have relevance in other scenarios.
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i would seriously consider buying the study materials for ms certification in Windows 2000 Server. they will have reference to more docs to help in Active Directory design...

See if this article will help:

http://www.microsoft.com/technet/prodtechnol/ad/windows2000/maintain/opsguide/default.asp
(please remove any spaces)