In Spring 2011, the New York Public Library (NYPL) launched one of the largest culinary data projects of all time: What's on the Menu?. The NYPL maintains one of the world's largest menu collections (around 45,000 menus dating back to the 1840s). The project aims to ease searching through this massive dataset. In simplifying menu search, What's on the Menu launched the first NYPL public API.
It's always exciting to see those outside the web industry using an API to improve their sites. NY Times First Look blog has a great example of what Dallas Public Library has done with the Best Sellers API.