This past weekend I stayed in Boston, in a lovely 1894 Victorian B & B on Beacon Street. The owner, Katherine Swanner, was a wonderful hostess and also a font of information about Boston, past and present. She mentioned that one of the primary ways people get around in Boston, besides the T (part of which conveniently runs right down the middle of Beacon Street), is by Zipcar, in which cars can be picked up for hourly or daily use at T stops and other convenient locations. Rockville has Zipcar too; I've written a blurb about how Zipcar works at Rockville Metro stations in the Greenpages.