My oldest son is starting to use his computer more and more as of late.  He has recently discovered the Super Mario Brothers clone SuperTux, and after beating all the levels has started experimenting with the built-in level editor to create his own.   The Google search built into his browser has made it so easy for him to start searching to find answers on doing that, among all his other interests (Webkinz, USB Funkeys, and whatever other commercial just happened to be on TV).  Prior to a recent upgrade to Ubuntu Gutsy on his machine, he used Ubuntu Christian Edition which uses Dan's Guardian parental controls.  I have been very happy with that, but the weakness is that it takes a blacklist approach, meaning only sites that have been added by Dan's Guardian will be blocked.  As good as they could possibly be, I can't count on them to catch everything.  On his new operating system, I was looking for a good solution and came across Glubble, which is a cross-platform Firefox plugin that allows parents to white-list known good sites and allow kids to only see sites that have been approved.  

I haven't set it up yet, but I just watched the video tour and it looks impressive!  If you are looking for a solution to this as I am, go check it out.  I will post back results after setting it up on his machine tonight.