Boston is served by an extensive and quite historic (it was the first in the United States) subway system known locally as "The T" (800-392-6100). There are five lines (including the new Silver Line "bus rapid transit), which runs to Logan Airport), and Park Street Station,, pictured here and located on the northeastern edge of Boston Common, is served by two of them, the red and green lines. Stops in some of the more gay-popular parts of the include Boylston and Copley in the Back Bay on the Green Line, Central and Harvard in Cambridge on the Red Line, and Back Bay and Mass Ave on the Orange Line. The new Silver Line "bus rapid transit" runs right through the South End, stopping at Mass Ave., Union Park, East Berkeley Street, and Back Bay Station.
The T system, which is operated by MBTA (Massachusetts Bay Transportation Authority) is generally a clean and handy way to get around, especially in combination with MBTA buses - it makes it so that you really don't need a car in this compact city (that also has very limited parking and can be a hassle for any driver, but especially one unfamiliar with Boston's narrow, crooked streets and frenetic pace). Unfortunately, the subway and buses shut down between around 12:30 and 1 am (depending on the line and the stop), meaning you're dependent on taxis, walking, or the charity of friends with cars if you need to get around late at night (bars in Boston are open until 2 am).