Northfield Mountain Visitor Center, Northfield, MA

I have only visited this attraction in the winter, so my experience is certainly incomplete. Parking is plentiful.
The exhibits at this visitor center are interesting. The whole mountain is "sponsored" by a utility company. Thus the exhibits are focussed on the economy of the Connecticut River - ice harvesting, logging, transporting good by waterways, etc. There's a real icebox that is ok to touch, and an example of an old logging tool, which, again you can touch.
A set of stairs lead down to a ski shop/vending area/restrooms (clean, nice). You may want to pause (endlessly, if you are my child) in front of a bank of birdfeeders in the bushes outside the window on the landing.
The yurt outside is awesome and had a fire going when we were there. It was toasty and cute in there.
In the winter the trails are groomed for skiing thus you cannot hike. The scenery is beautiful.

Northfield Mountain

Northfield Drive In, Hinsdale, NH

This is a great place to take the kids at least once per summer. A green and beautiful drive takes you up to Northfield (actually Hinsdale), where you can enjoy the parking lot atmosphere and have something to eat while you wait for dark. A large playground is provided (though it's pretty old equipment). Concessions are available but why not bring a spread of your own with everything that you like? If your kids start to cry during the movie, just roll up your windows and turn the movie's volume up on your radio. Eventually they will fall asleep and you can watch the rest of the double feature.

We are really looking forward to visiting again this year.

Northfield Drive In