Here's a few I've been to around New England:
Northfield Drive-In (Northfield, MA actually I think it's just over the NH line): Northfield Drive-In - http://northfielddrivein.com/#
Milford Drive-In (Milford, NH): Milford Drive-In, 531 Elm St. Milford, NH 03055 - https://www.milforddrivein.com/...