Apache can be configured to authenticate users against an LDAP database, such as Open Directory, part of Apple's OS X Server.
http://httpd.apache.org/docs/2.2/mod/mod_authnz_ldap.html
http://blog.case.edu/gps10/2005/02/23/apache2_ssl_ldap_authentication_howto
http://www.nies.ch/doc/apache-ldap-webdav.en.php
Prerequisites
yum install openldap-devel
Installation
To install LDAP authentication support in Apache, it must be configured with:
--with-ldap --enable-ldap --enable-authnz-ldap
NOTE: --with-ldap appears to be broken in Apache 2.2.9.
Might also need: