Call too late, visit too early

Now that my daughter is big into talking to her friends on the phone, we've had some conversations about how late it is acceptable to call someone you are not related to or who is not expecting your call. Before 10 p.m. is my rule, but even after 9 p.m. I feel awkward. (I don't even like hearing from family members much after 9 p.m., to tell the truth.) But something happened yesterday that made me think of another rule of polite communication that seems to need defining: What's the earliest time in the morning it's okay to show up at somebody's house? My son has a school friend who lives across the street from us on the alternate weekends he's living with his dad, and this kid (who roams the neighborhood way more freely than a control-freak mom like me can comfortably abide) showed up at our door at about 7:50 a.m. Sunday morning, just as we were rushing out the door to church. We told him to come back later, but that almost-playdate was enough to set my son on "I don't want to be in church" mode for the next hour. Who lets their kid go to a friend's house at 7:50 a.m.? On a Sunday? I'd say anytime before 10 a.m. on a weekend's pushing it, and then you should call first. But not before 9 a.m. (and even then, I'm liable to bark at you for waking me up). What are your time-and-communication rules?