Introduction
Eric Woods and Matthew Marum are implementing support for OAuth 2.0 in Apache Shindig. This article provides an overview of the implementation, including high level design, supported flows, common how-tos, descriptions of classes, and future considerations.
The OAuth 2.0 specification is here: http://tools.ietf.org/html/draft-ietf-oauth-v2-20
Note that the implementation is still evolving, so consider this design document to be a draft.
High Level Design 
Supported Flows
How-Tos
How to Register a Client
How to Add a Custom Grant Handler
How to Enable/Disable OAuth 2.0 Security
Description of Classes
...
This documentation lives on the Apache Shindig wiki: https://cwiki.apache.org/confluence/display/SHINDIG/OAuth+2.0+Service+Provider+Implementation+in+Apache+Shindig