For every bad one you add to your restricted list, two new ones pop up somewhere else on the internet that your kids might access. Basically kids can only visit a list of sites you've pre-approved. This prevents them from straying off into places you don't want them going. Another nice feature of Net Nanny is it's ability to restrict certain file types. Net Nanny is more than just an online defense, it also keeps things safe when your not connected.
Parents can limit what programs and areas of the computer kids can get to.
No one can protect your kids better than you can, so tell congress to screw off and get yourself Net Nanny.