The flickrj-android library is designed to wrap the Flickr API and provide improved support for Android and the Google App Engine. This library also supports Java 5 syntax and the new Flickr OAuth authentication model.
Mashup contests can be a good way to reveal the variety of applications that are possible when the developer community is provided with a quality API. At the recent BarCamp London 5, Stefan Magdalinski, CTO of MOO.com, ran a weekend-long MOO API hack competition. The MOO service and API let users submit custom designs that can be printed onto products like business cards, sticker books, postcards, etc. These products can then be sold through an online store.