Explaining deep technology
Documentation for a weather REST API.
Documentation for CityGrid REST APIs.
A guide for developers on writing API documentation, published in the Microsoft Developer's Network magazine. It was the most popular article of that issue.
Blog posting on how to write documentation explaining how your API uses OAuth.
Some best practices for writing Web API documentation.
Explains why Markdown is a good choice for API documentation.
Provides pointers on how to write good sample code for APIs.