OpenLDAP Software is an open source implementation of the Lightweight Directory Access Protocol.

The suite includes:

• lloadd – stand-alone LDAP Load Balancer Daemon (server or slapd module)
• slapd – stand-alone LDAP daemon (server)
• libraries implementing the LDAP protocol, and
• utilities, tools, and sample clients.

Also available from the OpenLDAP Project:

• Fortress – Role-based identity access management Java SDK
• JLDAP – LDAP Class Libraries for Java
• JDBC-LDAP – Java JDBC – LDAP Bridge Driver
• LMDB – Lightning Memory-Mapped Database

Find out more here.