Adrian Holovaty has created a very interesting website using publicly available information on crime in Chicago by putting data released from the Chicago Police Department onto maps with the Google Maps API.
This is a very useful useage of the Google Maps API. If I was from Chicago, I'd find this site very alarming and useful at the same time.
The site also has free RSS feeds for every police beat and every city block in Chicago. So you can monitor your workplace, your children's school, your home, etc. Data is a week old due to processing delays at the police department, but just imagine how useful this will be.
In Boulder, in the local daily paper, they publish a crime map - which is also alarming, given the size of the community. Lots of scumbags out there.
cdg