Popular API Examples
Perhaps host an up to date set of "popular" API's such as twitter, facebook whatever so that developers DONT have to write their own mocks and can just point their apps at this site to get quick "fake" response for popular existing APIs.
This does sound obvious at first, but we decided against this. An API documentation is something that the API publisher needs to take responsibility of.
If we are going to produce documentation on behalf of 3rd-parties, it’s going to become quickly outdated.
Rather then hosting bad, misleading documentation it’s better it doesn’t exist at all.