ISODE 8.0.1 for Linux:This is the source distribution of the latest free ISODE release patched for working with Linux. This contains the implementation of many OSI protocols over TCP/IP and QUIPU X.500 directory server.
CriticalPath InJoin Directory Server: The InJoin Directory Server X.500/LDAP directory server with support of SSL/TLS, SASL and X.509 authentication. There are several other directory-related tools from CriticalPath available
eTrust Directory: An industry's leading solution for large-scale, business-critical directory service applications.
NEXOR Directory: High Performance X.500/LDAP directory server build on top of an OO database and a WWW based management interface.
Solstice X.500 Directory Products: They enable companies to build a standards-based, distributed directory that offers a common storage space for data regarding people and resources.