If you are looking for more cities that just Boston, you should check out OpenStreetMap. http://www.openstreetmap.org/
People have been adding building outlines for many cities, some are better than others. People continue to add buildings individually, and sometimes complete cities are added when the data license from the administrative body is compatible with the license for OSM.
The data is free, and you would be able to distribute it under the CC-BY-SA license (Creative Commons, with attribution, Share Alike). Even better, as you and others improve the buildings data, you will always have access to the latest and most improved data.)
Washington DC: http://www.openstreetmap.org/?lat=38.89763&lon=-77.03236&zoom=15&layers=M
Not as good:
San Francisco: http://www.openstreetmap.org/?lat=37.7792&lon=-122.3935&zoom=14&layers=M
New York City: http://www.openstreetmap.org/?lat=40.71209&lon=-74.00249&zoom=15&layers=M