Around Boston...close....nothing that I know of.
Within driving distance of about an hour.....
Normandy Farms in Foxboro, MA on the south side is probably the best bet. Scusset beach state park on the cape cod canal offers nice recreation opportunities on the canal and a beach but no sewage hookups. Hampton beach, NH state park if no pets is about an hour out of Boston and you can be waterfront at the mouth of the Hampton harbor with full hookups. Salisbury beach MA state park is a bit closer than Hampton but not as nice as Hampton IMO.
Loads of places in Maine, try rvpparkreviews.com