We used the hop on, hop off bus in Portland ($5.00/person for the day) which was great. Recommend seeing the Fireman's museum, small but good (don't forget to talk to the volunteers there, that's what is so interesting).
We did do the Titanic Museum in Halifax, NS. Great experience. You'll see a deck chair and a pair of little girl shoes that were displayed among many other things. We didn't get the Big Pink Bus from the cruise line, but when we got of the ship we got tickets at the booth which was the same price as on the ship and they took the our seapass for payment. So, same difference. Get the tickets on the ship.