Some of my more popular blog posts are the ones detailing my work on modifying the acts_as_authenticated plugin to work with the open_id_authentication plugin, giving you both OpenID and username/password logins in your Rails application -- here, here and here. After a few inquiries, I have now updated my sample OpenID application to work with the latest Rails (2.x), the latest ruby-openid gem (2.0.4), and the restful_authentication plugin, and I've made it a free download at Rails Kits.
I've taken these two fantastic plugins, made some nips and tucks to get them working well together, and put it up for download at the OpenID Rails Kit page.
Getting started with OpenID on Rails is as simple as downloading the Kit, installing the ruby-openid gem, and loading the included schema. It even supports Yahoo's implementation of specifying a different identity URL than the one the user supplies when creating an account (part of the OpenID 2.0 spec), as discussed here.