Do you like beer?  Then the Atlantic Brewing Company in Bar Harbor is a great stop.
According to their website:

The Atlantic Brewing Company began as Acadia Brewing in 1990. At first the brewery was located inside the Lompoc Cafe in downtown Bar Harbor and had a maximum capacity of just one barrel at a time. Within a few years the demand for our beers had grown so much that we moved the brewery two doors down from the restaurant and increased our capacity to seven-barrel batches. However, by 1998, we had outgrown that facility as well and so we moved again – this time to our current location on the Knox Road. Our estate brewery was built on the grounds of a 19th century Maine farmstead, that employs native vegetation and local stonework.

 
They have several locations in and around the Bar Harbor area and offer tours and tastings.  Here’s what you need to know:
The have three tours daily from Memorial Day through mid-October.  Reservations are not required, but they can only accommodate 25 people per tour.    The tours are approximately 20 minutes long, followed by a tasting. Children are allowed on the tour, but obviously not the tasting.
The addresses are:  We are at 15 Knox Road, Bar Harbor, ME 04609 and 52 Cottage Street, Bar Harbor, ME 04609