LDAP

• ldap-binaries-and-commands
• configure ldap for centralized logins.
• hope this docs helps:

   http://www.openldap.org/doc/admin22/

   http://www.openldap.org/doc/admin/quickstart.html

   nice web way to admin an ldap server(make sure to secure it) - http://www.phpldapadmin.com/

   nice way to explore ldap stuff via a java app - http://jxplorer.org/

http://people.debian.org/~torsten/ldapnss.html