Seattle's Stranger did a neat feature. They sent reporters out to look for lights on at 3 a.m., and to ask those folks why they were up and what they were doing. (Link goes to main story, but other neighborhoods are featured in the colorbox.)
They actually didn't get very interesting responses, but I love the concept. I'm always wondering what people are up to at weird hours.
I actually think they would have had better, more diverse stories if they'd stayed out of the hip neighborhoods that they probably think of as their demo, and instead gone into more ordinary residential hoods. They went to Ballard, where I live, but they stayed right by the downtown part of the neighborhood, not up to my quiet, more family-centric region.