I've travelled to Maine, Boston, Plymouth, Salem, Nantucket, Martha's Vineyard: I was most impressed with Boston though - it was amazing to walk the "Freedom Trail" and stand on the same ground where the Declaration of Independence was read, Boston Massacre occurred, and even Paul Revere's ride. We also followed a Revolutionary War route - including visiting a home used as a pub at the time. It was cool - during the life of this home, past owners had drywalled the ceiling/walls - so when the drywall was removed during the renovation - you could still see the cigar/pipe smoke stains on the ceiling! I like to imagine what the topic of discussions were as the men sat around smoking their pipes.
Plymouth was really cool too - the reinactment camps are very interesting - and not at all hokey (which I half-expected after visiting Salem.) Plymouth Rock seemed over-rated and tourist-y though. The Wampanoag Tribe was AMAZING - we actually helped cook rabbit stew, build a fishing net and harvest corn. It was very cool. And - there was no corny "mold-a-rama" machine in site. However, the Dippin' Dots station was right outside the exit. Ah well, can't have it all...
Salem - you need to know where to go. If you go into some "museums" - you get a corny tour with some multi-pierced goth girl in pilgrim clothing. I felt the murders of these men and women were being too commercialized - so I didn't buy anything in any shop. It didnt' feel right to me.