The Readius rollable, foldable display device from Polymer Vision are being mass-produced for your enjoyment in their spanking-new facility in Southampton, England. Those stiff, flat screen devices like the Kindle and the Sony E-Reader are cool - but paper-thin is the way to go.
(Polymer Vision Readius display video)
The Readius is a small electronic document reading device that can fit easily into a pocket; the five inch diagonal rollable display unfurls when you need it. The device offers 3G high speed connectivity to news and information. As you can see in the video, it can also handle some degree of video display, which you can't do with the e-paper technology.
Science fiction fans have long enjoyed thinking about very thin, easily-stored displays. An example of a larger, rollable display is the poster tv from Larry Niven's 1976 novel A World Out of Time. See also the pocket-sized polycarbon phone screen from Idoru, a 1986 novel by William Gibson.
Update 16-Dec-2007: Thanks to Blue Monkey, we have this great picture of the rollable map display from the 2000 movie Red Planet.