A while ago, a UBC student, for his school work, made a digital scanning back out of a flatbed scanner.

Here is another implementation of that idea:
http://www.scannerphotography.com/ (site mirrored due to Slashdot effect http://hardware.slashdot.org/hardware/06/01/19/0137225.shtml)

What is interesting is that along a gallery of photographs, much more details are provided.