HTTP API design : This guide describes a set of HTTP+JSON API design practices, originally extracted from work on the Heroku Platform API.
Pro Git : The entire Pro Git book, written by Scott Chacon and published by Apress, is available here
JSON Schema : JSON Schema is a vocabulary that allows you to annotate and validate JSON documents.
Swagger : Swagger is a powerful open source framework backed by a large ecosystem of tools that helps you design, build, document, and consume your RESTful APIs...
CSSdoc : This is a draft to bring automatic documentation to CSS files, like its known for JavaScript and PHP files through JavaDoc/DocTags.