This came up in a thread a few weeks back. Thought I'd share the latest.
The ferry goes from Yarmouth, NS to Portland, ME. It goes each direction once per day. It's a long ride, and probably a lot of fun if you can afford it. My guess is it will be in the ballpark of $100 per person. Even so, it still beats the sheet out of driving the extra 750 miles.
Downside is that it only runs May-Oct so there is limited overlap with the best months. Plus, Yarmouth is more on the interior...you'd likely need to travel 40+ miles from the port to get to the more exposed areas.