The biggest things to keep in mind that the hours can't be done during class time (ie. during the regular school day, other than at lunch or after school) and that you can't volunteer for a relative (ie. babysitting your younger siblings or cousins, etc.). You also can't count anything that also results in a credit (ie. co-op) or anything for which you receive pay or that a paid employee would normally do.
There are lots of options, though. Your school's guidance office should have a record log booklet that your DD can pick up. I think there's a list of suggestions on the back of it. They also usually have a ton of opportunities posted on the bulletin boards there. The office is still likely open this week, depending on your school.
One suggestion, if she doesn't want to go on her own, is to make it a family event. Pick somewhere that needs lots of volunteers, like a food bank or a charity fundraiser or marathon or something, and go as a whole family to help out. That way, she's not alone with strangers, and still gets her hours. Or if the whole family can't go, does she have a cousin or close friend that also needs their hours? Maybe they could go together to something like that?
If she does end up on her own, the idea of something like the humane society is a good one. They usually need dog-walkers, and that's something where you're not really with the people there, you're outside with the dogs.
Your local public library probably also has kids' summer reading programs, and they often need older students to help younger ones with their reading...that's strange kids, rather than adults, so it might be less intimidating. Or, if you belong to a church or community group of some kind, they may have a need for volunteers, and that way, it's people she'll at least know in passing from other functions she's attended.
What can she do?
then helped us haul the tables and chairs back into the school. 
