calibre - Ebook manager, viewer & converter
Adobe Digital Editions - ebook reader software
FBReader - FBReader is an e-book reader for various platforms. Features:
Calibre Web - Calibre Web is a web app providing a clean interface for browsing, reading and downloading eBooks...
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Moon Reader - Innovative book reader with powerful controls & full functions