Acadia National Park is the place to go in Bar Harbor. It requires a rental car or organized tour, there is a trolley service as well. Very beautiful scenery, places to hike, bike, lakes and ponds, places to stop and enjoy the water, head up to the top of Cadillac Mountain for scenic view. It is a absolutely beautiful place to be in the summer. I live in NH and love going there myself. You can go to barharborinfo.com or to the National Parks site for more info.
We are doing our fourth cruise in Sept through this area. The advice you received on Bar Harbour is good. Also Bar Harbour itself is a lovely little town. It is full of great shopping. You can stroll through the town very nicely in the time alloted byt the cruise line. I love it there!
In Portland the cruise lines often run a shoppping excursion to a big shopping area. I can't remember the name of it but it is the home of Lands End stores and there is a regular retail store and a factory outlet store there. If you don;t like shopping, my husband found a great railway museum within walking distance from the dockside. He went there and I went shopping.
In Martha's Vineyard we enjoyed walking around the town. There is an area with old artisitc white lattice work (lace like) houses. They are really very special. We also walked along the waterfront and enjoyed that immensly.
There is a lot to do in Halifax. I personally have not seen this but others on our cruise last year went to an exhibit from the Titanic and said it was really wotrh the visit.
Most of the cruise lines also offer excursions to Peggy's Cove. It is a must see! Wonderful seaside area with an old ancient lighthouse way out on a rock. Great little village. Restaurant with fresh lobster if you are interested in savouring lobster.
The Halifax waterfront has been converted into "The Halifax Historic Properites"
It caters to those who want to just stroll the waterfront. It is really nice. The ship docks right here and there are signs pointing to it. Also there is Pier 21 which is the history of immigration to Canada. We actually went there and found the original paper work for my mother in law who came to Canada in 1926. We were also able to find the ship that she arrived on and get a picture of it. We brought it back to her as she is now 97 years old.
I could keep going as I love this area. We will be on the new Norwegian ship The Jewel
Sept 18-29. Back to this area that we love again!
Enjoy your cruise and hope this was helpful.