Epic NYT data visualization: New York City Homicides Map
Fine-grained data for every homicide in the city 2003-2011: Scrollbar at the top to show all years or any individual year. Click buttons in the left sidebar to show breakdown by month and time of day; race/ethnicity, sex or age (of victim or perp), weapon used;, or borough; each of which colors the graph accordingly. Zoom in and rollover any individual homicide to see the data for that one.
Would be interesting to have data going further back in time. Homicides have shown a more or less steady decline from 597 in 2003 to 209 in 2011. But consider that homicides numbered over 2000 at their peak in 1991: