Shuttle to Manchester Airport from Sullivan Sq. T and Anderson RTC.

it's actually pretty convenient, aside from the fact that it only runs every two hours. The service is particularly useful for those on the north side of the Charles, as it makes getting to Manchester Airport as easy as getting to Logan. It takes an hour and fifteen minutes to get there, assuming traffic is flowing freely.

http://www.flymanchester.com/transportation/shuttle_service.php

Oh, yeah, and it's free for ticketed passengers, although I've now ridden it twice in the last few weeks, and no one's asked for any evidence of that. I guess the suitcase kind of gives it away.