Fedora Directory Server
The enterprise-class Open Source LDAP server for Linux. It is hardened by real-world use, is full-featured, supports multi-master replication, and already handles many of the largest LDAP deployments in the world. The Fedora Directory Server can be downloaded for free and set up in less than an hour using the graphical console.
The link address is: http://directory.fedoraproject.org/

