New York City Homicides Map
The New York Times has created a Google Maps mashup showing the location of all 3,402 homicides in the city since 2003. The data has been collected from New York Police Department announcements, in addition to news accounts, court records and additional reporting.
The map is a great example of how a huge amount of data can be presented on a map using the Google Maps for Flash API.
The search options on the map are also really impressive. It is possible to view data for any year by using the slide bar at the top of the map. It is also possible to refine the data by month and time of day, race/ ethnicity of the victim, race/ ethnicity of the perpetrator, sex of the victim, sex of the perpetrator, age of the victim or perpetrator, weapon used and borough.