Movies.
Art or historical museums: Worcester Art, Danforth, Peabody Essex, tons more. Old Sturbridge Village, Plimoth Plantation, NE Aquarium.
Kennedy Library, Boston Freedom Trail, Duck Tours, seaport area, Boston Harbor Island tours, Public Garden (do the Swan Boats if you haven't in the last 20 years).
Outdoor sanctuaries like Garden in the Woods, the Butterfly Place, etc. Hike around Walden Pond. Road trip to western MA along scenic Route 2, check out charming Stockbridge and North Adams/Williamstown with parks, scenic views, museums.
Any of the fantastic free summer concerts at parks and other locations.
Do a paint night - those seem to be very popular lately.
Go antiquing up in the Conway NH area, take short hikes at the nature areas along the Kancamagus Highway, walk out on the rocks to the middle of the river, take the ski lift to the top of the mountain for a scenic view.
Poke in the shops at places like Kennebunkport or Rockport.
Cliff Walk and Newport Mansion tour. Pack a picnic and eat along the water (I know it's eating, but it's not as expensive as going to restaurants!).