Sea kayaking, small boating, and sailing are the best ways to poke around the multitude of small granite islands that fill Penobscot Bay. Hurricane Island isn't open to the general public, but Vinalhaven and North Haven are. Weather conditions are changeable here at any time of year. July and August are generally warm and dryish, so they are the peak months along the coast. Shoulder seasons can have decent weather as well, and the crowds are smaller then.
Major airports are in Bangor and Portland.
In the summer, a ferry runs six times a day from Rockland to Vinalhaven. Winter schedules vary, so call ahead. However, reputable outfitters or commercial tour guides can often take you to various islands. MITA has made arrangements with land owners to allow responsible access along the trail, which is some 350 miles long and stretches roughly from Portland to Machias, although it changes every year as islands change hands. One coastal island was actually quarried out from underneath the 146 stone cutters who lived and worked on the island.