Massachusetts - Moshup, in Aquinnah on Martha's Vineyard: a dozen or so trips, several days each trip. My favorite. Not officially a nude beach, but there has always been a crowd of at least a few dozen, and often several dozen, other naked folks, and the police don't bother us. Beautiful spot, warm(ish) water. A bit hard to get to, but I always bicycle. - Lucy Vincent in Chilmark on Martha's Vineyard: has an official nude section (I looked it up). The day I went, it was mobbed by parents in Lands End bathing suits with their kids, and I was the only naked guy on the beach. I felt like a sex offender, although I think I never did anything illegal. Not a great day. I went, took off my shorts, sat there feeling stupid for a few minutes, then got dressed and bicycled down the road to Moshup. - Longnook Beach in Truro on Cape Cod: Also not officially a nude beach, but public nudity is unofficially tolerated. It is really remote, and there was almost no one else there the day I went, which was a beautiful sunny weekday in July a few years back.
Vermont - Red Rocks Park in South Burlington: Vermont does not have a statewide law against public nudity, although disrobing in public is illegal, and the state also prohibits displays of nudity intended to shock or offend (or something like that), so this is kinda sorta an official nude beach. The day I went, a sunny summer weekday, it was nearly empty, and I was the only naked on there. That was weird.
California - Baker Beach in San Francisco: I went on a summer weekday. There were a few other naked people, mostly single guys, and a large crowd of clothed folks. The views are beautiful, the beach is nice, the water is freezing.