In this commit, this commit, this commit and this commit the Rails Core team shows that Engines in Rails are not as dead as once thought, and are making a comeback in (possibly) the next release which is either 2.3 or 3.0.
This is fantastic because when I’m asked if people can use rBoard they need to integrate it into an existing app, rather than having it stand alone. A lot of that would be massaging it all in to your app, but now you can have it as a separate plugin with it’s own app/* folders and config/routes.rb file too.