Poverty and Race in America, Then and Now lets you look at any metropolitan area in the United States and compare poverty in it in 1980, 190, 2000 or 2010. You can view the comparison on a “sliding” map, though I wish it just showed you the same locations in two screens — that would make it a little easier to compare to the two views (you’ll see what I mean when you visit the site).

I’m adding it to The Best Tools For Analyzing Census Data (even though the data also comes from additional sources).

Thanks to Google Maps Mania for the tip.