The Port25 guys have a really good paper on using Windows to manage Linux Identities. It relies on Samba on the Linux client side, Linux’s Pluggable Authentication Modules (PAM)  and Identity Management for Unix under Active Directory Services on Windows Server 2003 R2. The Linux client is made a domain member of the Windows Server.

The latest version of Samba (v4) is looking to provide a full Active Directory domain controller but I don’t think Microsoft will be writing a paper on this.