Okay, just found this on boingboing...someone has combined Google Maps with Census data from 2000. The result - you can look at the total population of just about any block anywhere. It even gives you the total population of any viewable area in Google Maps. My block, for example, occupies .0081 square miles, had a population of 136 in 2000, and has 84 units on it. My ZIP code is incorrectly labeled, but who's nitpicking?
And I'm pretty sure I've posted about this before, but I still want to read this guy's book, Shadow Cities...apparently he lived in squatter cities on four different continents and now he has a blog to write even more about them. Someone buy me this book, okay? Thanks!