calibre - Ebook manager, viewer & converter
FBReader - FBReader is an e-book reader for various platforms. Features:
tinyMediaManager - A multi OS media manager written in Java/Swing
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Delicious Library - Delicious Library 3: Catalog your books, movies, music, software, toys, tools, electronics, & video games. Archive your life.
Cool Reader - Fast and small cross-platform eBook reader for desktops and handheld devices