Not sure if this is what you had in mind, but Linux w / Samba can act as a domain controller for Windows desktops. For example, see SAMBA Server (Domain Controller) for small workgroups in HowToForge. This works for file / printer sharing, etc.
Something more like Microsoft Active Directory, you can check out Red Hat Directory Server :
Red Hat Directory Server is an LDAP-based server that centralizes application settings, user profiles, group data, policies, and access control information into an operating system-independent network registry.
If the issue is cost related, there is a version of Fedora Server whose community version is free.
Sun OpenDS project:
OpenDS - , LDAP DSML. OpenDS , , , .