Penguin is releasing six of their classic titles (including Emma, The Picture of Dorian Gray, and Crime and Punishment) with blank covers that are art-quality white paper so you can draw or paint your own cover image. On their web site they have a gallery in which they display the covers that readers come up with. (You can see that here.)
I don't know how many people will actually be interested in doing this (although making your own cover would make the book a much more personal Christmas present, for example). But I do know that this is getting Penguin some valuable press coverage.
In this case, the idea came from within Penguin, presumably the marketing department, but it could just as easily have been proposed by an author as part of his or her book proposal, especially if it were relevant to the topic of the book (e.g., a book on creativity, print design, or interactivity).
It's a great example of my mantra, 'do something different.' In fact, it has given me an idea for a promotional contest to help drive people to my website (www.timetowrite.com) and let people have some fun as well. You'll be the first to hear about it here soon, with an invitation to join in.