OCModShop posted an article series about building a Linux-based firewall

Kids today have more adult freedoms and priveledges than any prior generation. Add to that all of the unwarranted privacy they receive, and you'll see that any parent should be concerned about what their kids are doing online. It's in the news every week: some teenager who has committed suicide over Internet Bullying, kids being listed as sex offenders for broadcasting naked photos of themselves. And don't even get me started on how anonynimity emboldens angry teens to behave in aggressive, rude, and socially reprehensible ways... especially when many families today only have one parent in the house. Do you think kids would act this way if they knew someone was watching?

Building a Custom Firewall Part 1: Why?