Parks are arranged alphabetically.
Carver (near Cape Cod)
The authentic steam train is the star attraction here. Also includes some kiddie rides. Special events include the fall Cranberry Harvest Festival and the holiday-themed Festival of Lights. All aboard!
This place is so small, it barely qualifies as an amusement park. And it has seen better days. Having said that, Salem Willows (named for the stately willow trees that line its promenade) is located on a stunning peninsula, surrounded on all sides by the ocean. The circa 1926 carousel is charming, the cruise line is delightful, the buttered popcorn may be the world's finest, and you haven't truly lived until you've had a Salem Willows chop suey sandwich.
Six Flags New England
Agawam (near Springfield and Hartford, CT)
Major park with a great collection of coasters, including the highly acclaimed Bizzaro (Superman).
Affiliated water park: Six Flags Hurricane Harbor at Six Flags New England
TOMB at 5WITS
If you're looking for some unique fun in Boston, check out the TOMB attraction at the 5WITS venue. It's a highly interactive walk-through adventure chock-a-block with theme park and movie flourishes.