Similar to this post and this request, I'm creating a OAuth client in Drupal 7 but using OAuth2.0. There's an OAuth2 module with an unpublished Drupal 7 version that I've toyed with, but it's geared pretty exclusively for servers or proxies, not clients. I've started writing a skeleton module for an OAuth2 client implementation, but before I go any further I wanted to make sure I'm not just spinning my wheels. Are there are any good modules that either implement a web services client using the OAuth2 standard, or a template module that I've missed?
A year later, there is OAuth2 Server which provides the server part only, but has tests which are a good demonstration of client code in Drupal (using drupal_http_request()), so that code can at least be used as an example. The module documentation also tries to explain basic OAuth2 concepts and potential pitfalls.
It is also on drupal.org, but it is a sandbox and needs some review and support in order to be promoted as a full project: https://drupal.org/node/2138549