calibre - Ebook manager, viewer & converter
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
FBReader - FBReader is an e-book reader for various platforms. Features:
Adobe Digital Editions - ebook reader software
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Icecream Ebook Reader - Ebook Reader by Icecream Apps allows to read ebooks in several formats (EPUB, MOBI, FB2 and others). Download EPUB Reader for Windows.