rflickr is a Ruby implementation of the Flickr API. It includes a faithful reproduction of the published API as well as method encapsulation to provide more useful object mappings. rflickr features result caching to improve performance.
Earlier this year, ProgrammableWeb reported that the New York Public Library (NYPL) had launched the What's on the Menu API, the first public API released by the institution. The New York Public Library has just announced the launch of the NYPL Digital Collections API which allows developers programmatic access to the Library's vast collections of digitized creative works including manuscripts, historical maps, rare prints, photographs and much more.
Instagram is one of those early adopter favorites that quickly crossed the chasm to more mainstream users, at least within my social network. Take that popularity, mix it with an apparent desire to buy shirts, and it was inevitable that someone would use the Instagram API to create wearable mashups. In fact, there are at least three such services, each with its own twist.