calibre - Ebook manager, viewer & converter
Goodreads - See what your friends are reading.
Calibre Web - Calibre Web is a web app providing a clean interface for browsing, reading and downloading eBooks...
LibraryThing - A home for your books.
Amazon Kindle - Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
BookAuthority - BookAuthority collects the most recommended books on business, technology and science - as featured on CNN, Inc and Forbes