Hannah Arendt, On Violence (New York: Harcourt Brace, 1970). Arendt analyzes the distinction between power--the force on which states are founded--and violence, the means by which people sometimes seek to assume or to keep power. "To substitute violence for power can bring victory, but the price is very high; for it is not only paid by the vanquished, it is also paid by the victor..."
Geoffrey Canada, Fist Stick Knife Gun (Boston: Beacon Press, 1995). Canada is the director of the Rheedlen Center, a nonprofit program in New York City where he works with children. He grew up in the South Bronx; this book, subtitled "A Personal History of Violence in America", will help you understand how children, who after all are born innately good, are drawn into violence.
Lt. Col. Dave Grossman, On Killing (Boston: Little, Brown, 1996). Grossman is a soldier who starts from S.L.A. Marshall's famous conclusion that most American soldiers in World War II did not fire their guns at the enemy. He then examines the means by which the military has ensured much higher effectiveness in subsequent wars--and the social price we pay for this training in violence.
Konrad Lorenz, On Agression (San Diego: Harcourt Brace 1963). A well-written, entertaining and insightful analysis of the biological and evolutionary roots of intra-species aggression, which is kept well in check in most animals other than man.
The Center Against Violence Everywhere is a program run by East Baptist Church in Philadelphia.
An Analysis of Juvenile Homicides is a scholarly paper published last summer by the National Center on Institutions and Alternatives.
Voices vs. Violence is the National Mental Health Association's campaign to eliminate violence.
Working Against Violence Page coordinates many links to other anti-violence resources.