Web APIs and mashups are not only of interest to the developer community. There are also research activities that look at how to improve various aspects of API design as well as services' and mashups' implementation and deployment. If you are interested in a cutting-edge research that may influence the future of Web APIs, then you should look at series of workshops on Web APIs and Service Mashups.
RhymeBrain is a service made to help writers, or anyone else for that matter, find rhymes for words, make new portmanteaus, and alliterate well. When writing with figurative language, or writing poems, such a tool can be very helpful for a writer who's currently stuck. It might also be helpful for such things as computer generated literature, but for that, you'd want a robust API with full access to the database. Well, you're in luck, because it does indeed exist.