Goodreads, a social network for readers: http://www.goodreads.com/about/how_it_works
Scribd, a digital publishing and social networking platform: http://www.scribd.com/
Vook, sells digital books that inegrates videos: http://vook.com/
Google Books, search the text of millions of book, browse and download public domain books: http://books.google.com/
Simon & Schuster eBookstore: http://ebooks.simonandschuster.com/
Barnes & Noble Online Bookstore: http://www.barnesandnoble.com/ebooks/index.asp
Sony Reader eBookstore: http://ebookstore.sony.com/
Apple iBookstore: http://itunes.apple.com/us/app/ibooks/id364709193?mt=8
Amazon Kindle Store: http://www.amazon.com/Kindle-Books/b/ref=sv_kinc_1?ie=UTF8&node=1286228011
Internet Archive Open Library: http://www.archive.org/post/312815/digital-lending-library
Project Gutenberg free public domain eBooks: http://www.gutenberg.org/wiki/Main_Page
Graphic.ly, a social site for digital comics that also sells digital titles: http://www.graphic.ly/
Marvel Comics Unlimited: Subscription based digital comics: http://marvel.com/digitalcomics/
And finally, if you want to know more about how "The Elements: A Visual Exporation" was created, check out The Times' Technology blog.
