The OAuth community is dedicated to helping provide information on the proper use of the OAuth protocols through a series of articles on different topics.
While OAuth is not an authentication protocol on its own, there are a number of high-profile authentication protocols built with OAuth 2.0. This article seeks to expose common pitfalls and demonstrate how to do end user authentication using OAuth 2.0 in a secure and reliable manner.
OAuth 2 Simplified by Aaron Parecki describes OAuth 2.0 in a simplified format to help developers and service providers implement the protocol. An expanded version of this article is also available as a book.