In general, the APIs and export options are accessible upon appending
&output=format to a given URL. Below, you can find a brief list of the available APIs and export options, aside from RSS feeds.
All APIs are by the way also accessible by using the context (CTRL+Right Click) or the keyboard menu (CTRL+e) on their corresponding HTML page.
We would be happy if you could inform us about your projects based on the API, so that we can contact you in case of changes to the API.