YouTube for Kids
Thanks to Josh Harris for pointing out these sites:
YouTube can be a sketchy place (even for adults). I just heard about www.kideos.com a kid-friendly version of Youtube that divides videos by age group.
TotLol.com does the same thing--all the videos are moderated by parents. (I still wouldn't encourage you to let your kids roam around these sites unattended, but they could be useful tools for your family.)