The New York Times raided Netflix's queue data and came up with this:
It shows Netflix rental patterns by zipcode in twelve great American cities, plus Dallas. Shown above is the popularity of Gus Van Sant's Milk in New York City. They've got maps for the current top 50 rentals for every zip code in all 13 cities, which is kind of nuts.
A few patterns tend to recur. In particular (based on my limited knowledge of the geography of these cities, especially NYC, which I know best) a lot of titles seem to fit into one of three categories:
Movies that are popular in wealthy urban areas: the yuppie and hipster neighborhoods. Includes Burn After Reading, The Wrestler, Milk (they're not big fans in surburban Atlanta), Revolutionary Road (but suburbs, too), Rachel Getting Married, Pineapple Express, Vicky Cristina Barcelona, W., Sunshine Cleaning, Religulous, Man on Wire, and Mad Men: Season 1.
Movies that are popular in poorer or working class urban areas . Includes Seven Pounds, Twilight, Body of Lies, Eagle Eye, The Soloist, Wanted, Pride and Glory, Push, Obsessed, Transporter 3 (never heard of this franchise), The Taking of Pelham 123 (only 31st most popular in Pelham), and RocknRolla.
Movies that are popular in suburbs. Includes Gran Torino, The Proposal, Mall Cop, Taken (never heard of it), Defiance, Nights in Rodanthe (city people hate it!), Yes Man, Marley and Me, Last Chance Harvey, Australia, and Bride Wars.
Lots of movies don't fit any of those patterns, of course, including I Love You, Man, The Dark Knight, and Watchmen. New in Town is just hugely popular in Minneapolis and nowhere else. And The Curious Case of Benjamin Button is inexplicably popular pretty much everywhere.