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.
mod_ispman is an apache module that interfaces with ISPMan (http://www.ispman.org/). It will take care of virtual hosts, authentication and authorisation. It will maintain a local cache to keep hits on the LDAP server low and performance up.