Contra dance is a light-hearted and easy-to-learn social dance, sharing roots with both square dance and English country dance. Every evening features a live band (somewhere on the folk/bluegrass/Celtic spectrum) and is led by a caller who walks through the patterns for each dance (there's also a beginners' lesson at 7:30). You don't need to bring a partner - there will be plenty of people to dance with. Come as you are!
Here's a video of contra dance in action: https://youtu.be/yQNE2nTBxVY