Take a look at Ruby on Rails Tutorial (http://www.railstutorial.org/). The sample application, a tiny Twitter clone, is designed to be fully up-to-date in coding style (though of course it reflects some of my particular idiosyncrasies). I just finished the Rails 2.3 book last week, so a definitive version of the source isn't ready yet, but there will be one eventually. (I'm focusing on the Rails 3 version first.)
On the other hand, if you want to follow the tutorial and make a definitive version of the code yourself (preferably with tags for each chapter end), I'd be happy to throw it up on GitHub. And you might just get a nod in the acknowledgments. ;-)
On the other hand, if you want to follow the tutorial and make a definitive version of the code yourself (preferably with tags for each chapter end), I'd be happy to throw it up on GitHub. And you might just get a nod in the acknowledgments. ;-)