I'm kind of surprised there is no maintained plugin which can get me out-of-the box personal messages system.
The only two close things google cames up with is GitHub - psergi/acts_as_messageable: private messaging plugin for rails plugin (I would love to have some generic views also created for me, but this one doesn't seem to offer that).
And pretty old tutorial http://www.novawave.net/public/rails_messaging_tutorial.html .
And that's it.
I guess my only option then is to cannibalize some other open source project to get required functionality, but that is also on the verge of "better to write my own"?