Let me start this post with a disclaimer - in the Colorado Real Estate Commission buyer agency agreement (sec 25), the contract plainly states that it is the buyer's responsibility to figure out who your neighbors are and whether or not you are comfortable with that. When it comes to neighborhoods, buyers (and not agents) make the call.
Simply speaking, Crime Reports lets me type in a physical address and then asks me what kinds of crime I'd like to be made aware of. Each week, I get an email report showing law enforcement activity that has occured in my neighborhood. Not always pleasant, but very, very valuable information.
Keep in mind that Crime Reports data is pulled from public records and may not always be complete or 100% accurate. But it's a good starting point for knowing what's happening in different neighborhoods and areas.