You can always count on Mark Rosefelder for nifty stuff, whether his own or someone else's; in this case it's a map of the US with areas that support various baseball teams in color. If your favorite team is lagging, or if you live in an area where that team's not well-represented, go and vote. Personally I'd love to see one of these for (American) football too; I'm told that the Steelers are the only NFL team that have a "dedicated" sports bar in every other NFL city, and it'd be fascinating to see how that worked out in practice. Oh, wait: further digging reveals that there is in fact an NFL map.
Even further poking discovers that this is part of a larger project to find out where people think they live, as opposed to where lines drawn by the government say they live. Very neat, and the US map thus produced is slightly but significantly different. Everyone go fill out their survey, it totally rocks. This is the kind of project that just couldn't have been done before the Internet. I love it.