http://www.howtoforge.com/running-vhosts-under-separate-uids-gids-with-apache2-mpm-itk-on-ubuntu-9.04
http://mpm-itk.sesse.net/
http://blog.stuartherbert.com/php/2008/04/19/using-mpm-itk-to-secure-a-shared-server/
http://wiki.apache.org/httpd/DifferentUserIDsUsingReverseProxy
http://wiki.apache.org/httpd/RunningMultipleApacheInstances