Researchers at the Human Multimedia Lab at Queen's University, Canada have developed two functional paper computing devices: Paperphone and Snaplet. What's novel is the use of bending the flexible displays to provide input. For example, bending the top corner of the paper phone is 'go to next page' when reading an e-book.
However, what made my mind boggle was the UI challenges for the Snaplet. If it is bent around your wrist, it acts as a super duper watch / media player / calendar, etc. If you take it off your wrist and it is flat, then it converts to a note-taking tablet.
Here's a video of switching between the two modes.