Chicago's WBEZ has created an interactive map of the city and where its various gangs operate, using data provided by the Chicago Police Department. Chicagoist considers the map and its implications while Progress Illinois discusses the changing nature of gang violence.
NextBus uses GPS to tell you the predicted time of the next bus. Google maps show buses in real time, and you can get updates on your phone/PDA. The coverage is limited to certain agencies within the US, so these other sites might be useful: Hopstop covers subways and buses in NYC, Boston, Chicago, San Francisco, DC, and more. (mobile version) Google Transit has many US metro areas in addition to Canada, Europe, and Japan. (previously) Many more locations inside. [more inside]
"Ok, my eyes must be deceiving me. That can't be someone aiming a gun at someone else on Google Maps Street View", says Michael Beck.
As a public service, tagged mapping can be used for much more than finding pizza parlors and Craigslist rental entries. Here it gets used to plot criminal activity, like bike thefts and other crimes in West Philadelphia and the larger Philadelphia area, as well as Chicago.