Hi - My daughter goes to Sudbury Valley School in Framingham, MA. It is truly a democratic school. The weekly school meeting sets and enforces all the rules. Every child has one vote, and each staff member has one vote. There are lots more kids than staff members, so the kids have lots of say in what goes on.
You ask what kind of activities they do with the kids. The kids initiate all the activities. The staff is actually very careful to make sure the initiative comes from the kids, and really only provide guidance when asked.
From what I can see, there is lots of art, music, games, and tons of outdoor play going on. Kids of all ages play together and learn from each other. There is a pretty big garden, and my daughter enjoyed lots of gardening activities this year. It is very different from any other school I've every seen, and I'm really very happy that my daughter goes there.
Hope that helps.