I run a newsletter all about APIs called GET PUT POST (https://tinyletter.com/getputpost).

Each edition features a Q&A with a company about their API and killer app ideas for developers. Here's a recent example with a YC S16 company called Nova: https://getputpost.co/an-api-that-unlocks-global-credit-data...

A few people have reached out about sponsoring it, but just for fun right now :)