Windows 7 | Active Directory Lightweight Directory Services (AD LDS)
Windows Server admins may want to look at this: http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=a45059af-47a8-4c96-afe3-93dab7b5b658
Overview
AD
LDS is a Lightweight Directory Access Protocol (LDAP) directory service
that provides flexible support for directory-enabled applications,
without the dependencies that are required for Active Directory Domain
Services (AD DS). AD LDS provides much of the same functionality as AD
DS, but it does not require the deployment of domains or domain
controllers. In environments where AD DS exists, AD LDS can use AD DS
for the authentication of Windows security principals. You can run
multiple instances of AD LDS concurrently on a single computer, and
have an independently managed schema for each AD LDS instance.