Bureau of Justice Statistics (BJS)
Quick access to a variety of data including crimes and victims, criminal offenders, law enforcement, courts and sentencing, prosecution, corrections, federal justice, expeditures and employment, etc.
Sourcebook of Criminal Justice Statistics
This source "brings together data from more than 100 sources about all aspects of criminal justice in the United States. These data are displayed in over 600 tables."
Uniform Crime Reports (UCR) - from FBI
"A nationwide cooperative statistical effort of nearly 17,000 city, county and state law enforcement agencies voluntarily reporting data on crimes brought to their attention."