We use NetNanny. Works really well, plus you can indicate specific sites that might not normally be blocked to be blocked.

Saddest thing is we had to start using it when we realized that the babysitter over the summer was POSSIBLY doing some things that were not cool on OUR computer!!

We have almost 9 and 7 y/o's. The 9 y/o is a computer game/video game nut. He loves Ruinscape online--and we allow it because he has some friends that play online and they will chat. But, we monitor it closely to make sure that he's only chatting with kids we know.
Recently, he bought Age of Mythology--which can be played online, but we do not allow that one yet to be played online. We limit the RPG to 30 minutes a day. We allow him to play on Nick, Cartoonnetwork, PBS, etc. for longer, but the RPG is 30 min.

The 7 y/o doesn't like the computer games and video games much--so it's not an issue w/ him.

oh, and NO WEBCAM at our house. Probably won't have one for a LONG time.

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Mental that one, I'm telling you. ---Ron Weasley, "Harry Potter and the Chamber of Secrets"