Seems like they are just starting out, but when I wanted to get information about police activity in my neighborhood, I spent some time looking at all different places. Everyblock.com seems to stand out on the way they are trying to aggregate the information and report it. They are pretty much only working with police reports now it seems, but hopefully they can grow into something more.
They are live in some other major cities across the US and seem along the lines of Yelp in the type of value they want to bring. The iPhone app is also a nice addition and actually has a better interface to what I want to see then the website itself, but that is another matter.