My friend and partner in crime Nicolas Grenié (@picsoung), and operator of our open source API search engine APIs.io, just let me know that the Taiwanese government just added an APIs.json file for their government open data site. Adding to the other authoritative (added by owner) government API indexes like from Trade.gov in the United States.
We haven't' had a lot of time to move forward the APIs.json index lately, but honestly it doesn't need much pushing forward at this point in time. Our primary objective is to continue getting adoption like this, and not radically shift the specification until we have more feedback from the community, across a large number of API operators.
You can learn more about the specification we've been working on over at apisjson.org, and see other existing implements from Fibit, Plivo, and Actuity Scheduling. Once you've created an APIs.json definition for your API operations you can add to the APIs.io search engine using the submission form, or using the APIs.io API. We are gearing up for another push forward regarding tooling being developed on the specification over the holidays and will have more information in 2017.