Centre for International Crime Prevention (CICP)
CICP is the UN Office responsible for crime prevention, criminal justice and criminal law reform.
Crime Statistics by Country (NationMaster)
Coverage is for a variety of topics including: assault, theft, corruption, counterfeiting, drugs, homicide, gun violence, human trafficking and more.
United Nations Office on Drugs and Crime (UNODC) Data and Analysis
Coverage includes: crime, corruption, drugs, human trafficking, money laundering, transnational organized crime, crime trends and more. A good jump off page is their data page.
Crime in the United States
Annual FBI Crime statistics for the US.
The NCJRS Abstracts database is a great place to search for criminal justice related information covering US and international sources and issues. Some are available as Full-Text.
UN Interregional Crime and Justice Research Institute (UNICRI)
The UNICRI Documentation and Information Centre has a comprehensive collection of data.
UNODC Homicide Statistics
The dataset covers 207 countries and territories and provides data on homicide levels, trends and contextual characteristics.