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 the RhymeBrain API does indeed exist.
The RhymeBrain API is quite simple, yet beautiful. Responses are formatted in JSON, and there are no API keys to be had or authentication to do. Your only limit is the rate limit of 350 accesses per hour. The alliteration function of the site isn't yet in the API, but it does offer something that might be more useful to a program, although not to a user on the site directly: word lookup. The word lookup function tells you everything the database knows about a word, including how it's pronounced, if it's a commonly known word, and if it's a vulgar word in the database's opinion.
Here's a "hello world" from the documentation:
"pron": "HH AH0 L OW1",
Flags relate to information available about the word. Offensive words are flagged "a." Common words flagged "b." And when the site is confident about the pronunciation, it's flagged "c."
Something like this could be extremely useful in natural language processing, or in creating such things as computer-generated poetry. It's work like this that brings us closer and closer to having programs that truly understand the nuances of language. You can also read more about this at the developer Steve Hanov's Blog.