TiVo has announced a new parental control feature called KidZone, standard for those with TiVo Series2 recorders starting June 2006. KidZone will do two things: it will simplify selecting family-friendly shows for kids to watch, and it will password lock all non-KidZone programming, so kids can't watch non-approved shows. GearLive has more detail about KidZone, and Thomas Hawk has plenty to say about it as well.
DirecTV/TiVo users (of which there are over 2 million, one of them being me) are out of luck; KidZone won't be available on DirecTV boxes.
[Thanks to Thomas Hawk and Rohit for the heads-up.]