http://www.liberiangeek.net/2010/05/the-perfect-parental-control-for-ubuntu-10-04-lucid-lynx/

http://www.linuxplanet.com/linuxplanet/tutorials/6584/1

Open dns

http://www.iuselinux.com/2009/04/parental-controls-in-ubuntu.html

http://ubuntuforums.org/showthread.php?t=843510