<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Dorlee:
Ports of call are: Boston;Bar Harbor, ME; Halifax, NS; Sydney, NS; Quebec; Saguenay; St. John, NB; Portland, ME; ending in Boston.</font>
In Bar Harbor, you don't need to go on an excursion. Once you get in town, you can take the Island Explorer bus service which is absolutely free. It will take you all over the island as there is more to Mount Desert Island than merely Bar Harbor.
Like Acadia National Park! It runs through October 13.
http://www.nps.gov/acad/bus.htm
Once you dock in Portland, you are in the heart of one of my favorite small cities. You can walk everywhere. You don't need to go on a bus tour. Meander through the small streets, wander into stores, enjoy some great seafood.
As for Boston, it's up to you. You can get anywhere you want via public transportation so if you have a good guide book, you can meander the Freedom Trail, go to the Museum of Fine Arts, stroll through Boston Common and the Public Garden, visit Fanueil Hall and Quincy Market, and tour Fenway Park. I personally wouldn't use a tour bus in Boston.