IBM Tivoli Directory Server

IBM Tivoli Directory Server provides a powerful Lightweight Directory Access Protocol (LDAP) identity infrastructure that is the foundation for deploying comprehensive identity management applications and advanced software architectures like Web services.

http://www.ibm.com/software/tivoli/products/directory-server

Open LDAP

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

http://www.openldap.org

Sun Java System Directory Server

Sun Java System Directory Server is a component of Java Enterprise System and delivers a user-management infrastructure for enterprises that manage high volumes of user information. It integrates with existing systems and serves as a centralized repository for storing and managing user profiles and access privileges, as well as application and network resource information.

http://www.sun.com/software/products/directory_srvr/home_directory.xml

Windows Server 2003 Active Directory

Windows Server 2003 Active Directory is a central component of the Windows platform. The Active Directory directory service provides the means to manage the identities and relationships that make up network environments.

http://www.microsoft.com/windowsserver2003/technologies/directory/activedirectory/default.mspx