Orono Brewing has a taproom in Bangor now. Outside of that it's "meh" city for breweries. Nocturnem and Blaze have the best tap/bottle lists. Be sure to look at the bottle list at Blaze... I've found some hidden gems [Farm to Face 14' at cost, Vanilla Rye a couple summers ago]
Hogan Road Deli, Bangor Wine and Cheese and Burby and Bates up in Orono are far less picked over than the bottle shops in Portland so you will often find some random goodies that are long gone everywhere else.