Quick note for trips to Salem and/or Providence, RI on the weekends without a car. MBTA Commuter Rail (which serves both) has a $10 weekend pass, good for unlimited travel Saturday and Sunday. Even if only going to one of those by commuter rail, it's less expensive than the weekday round trip fare.

https://www.mbta.com/fares/commuter-rail-weekends

(It is not valid on Amtrak trains between Providence and Boston, though sometimes those tickets are very cheap since they're just getting additional $ for seats sold between NYC and Providence.)