I had Netnanny and SafeSurf at one stage. Too restrictive for my teenager. So tried Dan's Guardian in my IPCop firewall/router. Too buggy.

Now I just rely upon their own discretion (and keep a wary eye on my router logs. ). Have only had to have one discussion with my 10yo about unsuitable sites. He normally just surfs the game cheat sites. My 14yo dau seems to be pretty good with whats she surfs.

Cheers
Mick