Curly and I are Burners, so one the highlights of our year is a regional Burn. Clothing is optional there and she happily runs around topless. Nudity is common.
We just made the event adults-only this year, due to legal concerns. Not with the nudity--with the sex. Public sex is not unheard of at the Burn as an avenue of self expression. That's a sticky wicket we want no part of, so we just made the event 18+.
The site where we hold the Burn is a year 'round campsite that hosts lots of Pagan events. Part of it is clothing-optional the whole year. There's another Pagan camp near the city that I hear is the same; I've not been to it yet.