Using Samba as a PDC (Primary Domain Controller) or BDC (Backup Domain Controller) is a very useful thing if you live in a mostly Unix world with some Windows clients. Samba allows you to use a Unix box as a PDC or BDC and Samba 3 allows you to use Samba as an ActiveDirectory PDC (Member Server?). With Samba 3 you can also use OpenLdap as the backend user database.
See also: OpenLdap, UnixPrinting
Documentation
General Samba Information
Fantastic Collection of Samba Tips
Samba LDAP Integration
Samba PDC
smb.conf (sample configuration file)
Samba Printing
Tools and Utilities
Manage user/groups stored in OpenLdap