THIS THREAD IS OUTDATED, PLEASE SEE http://ubuntuforums.org/showthread.php?t=843510 FOR THE CURRENT VERSION OF THE SOFTWARE
Here is a simple (but powerful) install script for a parental control feature
It is based on tinyproxy + firehol + dansguardian and on an howto found on this forum (dunno remeber where)
Download the attached archive, extract it and run the script (2x click or from a terminal) (There are a couple of hidden files and folder too in the archive)
It will d/l, install and configure all you need + install a GUI created by me to configure everything (it is located under System --> Administration)
Please report any bugs.