Quick, what is your House of Representatives district? Many people don't know this number, or the member who represents them. The New York Times' new Districts API makes it easy for your application to answer the question for any point within New York City, though it could serve as a template for a nationwide--or even international--service.
Our API directory now includes 82 address APIs. The newest is the 1Map API. The most popular, in terms of mashups, is the geocoder API. We list 41 geocoder mashups. Below you'll find some more stats from the directory, including the entire list of address APIs.