Lightweight Directory Access Protocol
LDAP defines a relatively simple protocol for updating and searching directories running over TCP/IP.
http://en.wikipedia.org/wiki/LDAP
- A Wiki that's all about LDAP: http://www.paldap.org/ (PALDAP: A Lazy Directory Administrator's Pal)
- An OpenSource implementation is at http://www.openldap.org/ .
ChrisBetts has a JavaLanguage LDAP browser client: http://jexplorer.org/