Free Internet Filtering Options
As a parent with kids who are more and more interested in the internet, I have become more and more interested in installing a content filter on the machines they use, but without having to pay as much as we do again for Internet access in the process. I have discovered K9 Web Protection as a good option for our Windows machines (and for you Mac elitists, there is a Mac beta, too), while DansGuardian has been a viable option for our Ubuntu Linux machines.
Of course, there is no substitute for parental supervision and involvement, but these programs can be useful safeguards as part of that process. Hope the suggestions prove helpful!