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.
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/.
The NSS LDAP Module allows you to do user authentication via LDAP. You can get it from: http://www.padl.com/nss_ldap.html.
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/.
A KDE based LDAP browing tool with the ability to edit objects (basically an LDAP admin tool). You can get it at: http://www.mountpoint.ch/oliver/kldap/.
A GTK based LDAP client that can modify settings/rtc. Available from: http://biot.com/gq/
A www based admint ool for LDAP. Available from: http://igloo.its.unimelb.edu.au/LDAPExplorer/.
A variety of Software Development Kits for LDAP, available from: http://www.mozilla.org/directory/
Written by Kurt Seifried