Murders in Boston
Mashups and Google Maps allow interesting visualization of data, making things suddenly more concrete. Dorchester has a reputation as being one of Boston's toughest areas: this map of 2008 murders in Boston brings it home.
Cambridge has a relatively low murder rate, though I haven't been able to find a similar mapping of murder stats. From a quick search, anecdotally I think it's been a couple of years since the last murder in Cambridge, though there have been recent homicides which appear to be accidental. Somewhat bizarrely, someone originally from Cambridge was recently killed in Salem. The method of murder?... being run through with a sword.