mod_psldap is an Apache module for leveraging LDAP services built on the OpenLDAP library and the Apache APIs, to include web based A&A, web based updates to the LDAP store, server-side XSLT processing, and session management across servers.
ISPMan is a system to design massive ISPs using LDAP as the backend.
ISPMan provides a web front end and a command line interface to create virtual domains and manages users, dns information, email infos and httpd setup data for these vhosts.