Lightweight directory access protocol seems to be the future of storing user information (passwords, home directories, phone numbers, etc.). Many products (ADS, NDS, etc.) support LDAP interfaces, making it important for Linux to support LDAP as it will be required to tie it into future enterprise networks.
LDAP servers
OpenLDAP
OpenLDAP is a completely opensource (note it is not GPL) package that provides an LDAP server, replication server and utilities. You can get it from: http://www.openldap.org/.
LDAP tools
ldap-client-cgi.py
ldap-client-cgi.py is a Python program that runs as a cgi and provides a www interface t an LDAP directory. You can get it: http://sites.inka.de/ms/python/ldap-client-cgi/.