Wikipedia -- http://www.wikipedia.com -- and the more specialized wiki sites it has spawned are excellent examples of Internet resources created by large numbers of individuals working together virtually. These volunteer collaborations have replaced printed encyclopedias for most people, and might be considered to be the largest, most dynamic open-access e-books in existence. Most users wouldn't consider these websites to be books, even though the printed equivalents certainly were.
An organization called "Distributed Proofreaders" (DP) is an aggregation of volunteer effort clearly focused on e-books. Many of the digital texts in Project Gutenberg have been produced by DP volunteers who check and correct OCR transcriptions of scanned books. While OCR (optical character recognition) can be very accurate for modern books, books and magazines printed in the nineteenth century and earlier present a variety of challenges. The resulting digitized works are dedicated to the public domain.