I've done everything from soup kitchen, to hospice to tutoring. It all depends. Maybe ask the center for student engagement @ your school for leads in you have one there. Otherwise check out with the predent/med/pharm groups at your school, they are most likely doing something to rake in those hours.
Personally I would try to volunteer in things that actually have meaning for you, or at least are interesting in some way.
For example, I love nature, earth, the environment, etc, so I volunteered planting trees and doing beach clean-ups, etc, did some stuff in support of a few diseases that have affected family members. This way not only will you get into it more and feel even better doing it, but if it comes up you'll be incredibly genuine and more passionate talking about it.
I worked with transfer students helping them on their first quarter on campus to make connections and find resources. I basically taught my own small class. I took them on tours around the campus, helped them make a plan of what to do by the time they graduate. I am a transfer student myself, so that's why I chose it.
I volunteer as a dental assistant at a free clinic that provides free dental services. It's really rewarding, great experience, and I'd recommend it to any interested pre-dent!
You can do almost anything. How small is your town? There probably isn't a homeless shelter/soup kitchen if its too small. Do you have a food pantry? They might need help stocking the shelves or making up bags to be handed out. You can volunteer to do some repairs at an elderly person's home- many churches know of people in need. Volunteer to tutor kids at a local school, help coach a sport you love, etc. The main point is to become aware of the needs in your community.