The New York Times just released an interactive map titled Mapping Homicides in New York City [nytimes.com]. Nowadays, it is quite refreshing to see a mapping application not directly based on the Google Maps API.
The data is compiled from open-records requests and major crime reports from the New York Police Department, including most homicides, in addition to news accounts, court records and additional reporting. The map will be updated as new information becomes available. Users can filter the data by month and time of day, race/ethnicity, sex and age of the victim or the perpetrator, the weapon used, or the borough the crime happened in.
The accompanying news article suggests that New York becomes a more lethal place in the summer months, although the dominant and most important trend involving murder has been the enormous decline in killings over the last 15 years, to levels not seen since the early 1960s.