Matthew Gagnon has put together some cool maps showing the difference between the last gay-rights victory in Maine (when an anti-discrimination law was upheld in 2005) and last week's defeat for gay marriage. The dark-brown communities on this map are places that switched from "pro" to "anti" gay. (I know it's not that simple, but I agree with Gagnon that these cities and towns made the difference in the outcome.) The red line represents Interstate 95.
As Gagnon notes, "The people who were receptive to voting for gay rights in 2005, and thus open to a good argument, but voted against gay marriage in 2009 were middle class suburbanites in the small to medium sized satellite towns that were within striking distance of larger cities and transportation corridors." It's great analysis; go read the whole thing.