Emmons, William, ed.  Transcript of the Trial of the Soldiers (1824).

Hansen, Harry.  The Boston Massacre: An Episode of Dissent and Violence. (Hastings House, 1970). [This book contains numerous factual inaccuracies.]

Kidder, Frederic.  History of the Boston Massacre.  (Munsell, 1870).

Zobel, Hiller B.  The Boston Massacre (Norton, 1970). [Zobels' book is considered the definitive treatment of the massacre and trial.]

Internet
Boston Massacre Trials (Massachusetts Supreme Judicial Court Historical Society)
This well-designed site includes essays about the trial and subsequent events, as well as biographical information and several images.

Boston Massacre (iBoston)
This site includes information on Massacre-related sites around Boston.

Crispus Attucks and the Boston Massacre
This site focused on the African-American victim of the massacre, Crispus Attucks.

Boston Massacre (Historywiz)
This site contains information on the Paul Revere engraving depicting the massacre.

Video

Discovery Channel.  Unsolved History: The Boston Massacre (2003).