Lots of people know & love the Chicago Crime website, the innovative early Google Maps mashup by Adrian Holovaty. Less well-known is the Citizen ICAM database run by the Chicago Police, which is the goofy-interface, balky, and hard-to-use lookup engine upon which the Chicago Crime website is based. As Adrian notes on his site, without Citizen ICAM there would be no www.chicagocrime.org.
Anyone who’s interested in the history of technology would enjoy reading this PDF from the National Institute of Justice. Dated July 1996, it is a very thorough account of the creation of the software that underlies ICAM and also has some good info on how they used it when it was just a PC-based tool based on MapInfo 2.0 only available inside police stations.