Delaware's New Castle County has added a Crime Map to their Public Safety pages.
It's interesting, but a little confusing. On first looking at it, I thought I was in a crime free zone, because there were no crimes listed in the area where I live. Looking back at the Crime Mapping FAQ page, I noted that it only shows crimes within the jursidiction of the New Castle County Police, so my Newark neighborhood isn't included.
It also doesn't tell you anything about the crime itself, other that whether it was a Homicide, Burglary, Vehicle Theft, Criminal Mischief, or Theft. Having a sense of when these crimes might have happened could be helpful. Are the ones showing something that happened within the last week, or month, or year, or decade? The FAQ tells us that these are crimes that happened within "the three month period dating back one full month prior to the current date" So, if it is January, this will show crimes from the previous September, October, and November.
It's a good idea, and I think I'd like to see it developed some more. I looked around at some other mapping programs set up in other places, and the City of San Francisco has a CrimeMaps program that is pretty nice.
There are a few people who have used Google Maps to develop some Crime Mapping programs. The first of them was Chicagocrime.org. Some others have also emerged, and a blog that discusses Google Maps points to some of those Crime Maps.
The stated purpose behind the New Castle County Police Crime map is to show "general crime trends to the community." To some degree it does that, though a "trend" is something that allows for the measurement of change over time, and this doesn't allow for that. It's easy to criticize, however. Getting a map online is a good start.
One concern noted in the FAQ page is for the protection of victims' identities, which is why the map only shows the "blocks" in which crimes have happened, rather than specific addresses.
Government Technology has a writeup of the Chicagocrimes.org site titled Modern Mapmaker which describes a little about the use and creation of their map, and the site has received a lot of additional press. It makes me wonder if someone from New Castle County, or the State of Delaware would be interested in finding out more about how those folks created their map. It has a very usable mapping interface.