Gosh, I wish I could pace myself with these amazing web finds but they all sprang up on me today, on a Sunday! Well, this one is slightly more digestible (compared to THE UNIVERSE down below). You can click on neighborhoods in New York and see an interactive breakdown of incomes (divided into categories: Extremely Low, Very Low, Low, Moderate, Middle and High). Its pretty spectacular.
Tip: Click on a neighborhood. In the little black box where is shows statistics, click "Who can afford to live here?" and some awesome rent sliders come out. You'll understand what I'm talking about... When you do it.