Recently I had a chance to work with Oauth and Rails using oauth-plugin and mongodb. Although oauth-plugin itself has a documentation but actually doesn’t cover the mongoid part detailed enough. Also I found this very good tutorial but it’s for SQLite3 only: Oauth Provider, Oauth Consumer
Base on the above posts, to get Rails and oauth-plugin working with mongodb, you need to do some changes.
Firstly, create a oauth-sample directory, you’ll put provider and consumer apps in there.