Some of the references you'll find in this section are a little dated, mainly because the technology was well-established some time ago, and thus most of the subsequent coverage has been focused on commercial applications.
1. As is often the case, Wikipedia has a strong entry on the technology behind "Electronic paper."
2. Displays to Keep an Eye On
(From The Economist, Mar 8th 2007 - subscription required)
The article provides a good overview both of current implementations of ePaper, but more broadly of other emerging display technologies (although most would not qualify as ePaper, per se).
3. Sony Develops Video Display So Thin It Bends Like Paper
"In the race for ever-thinner displays for TVs, cellphones and other gadgets, Sony may have developed one to beat them all - a razor-thin display that bends like paper while showing full-color video."