Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
AlReader - Alreader.com - new perspective on reading e-books.
calibre - Ebook manager, viewer & converter
Universal Book Reader - Just like its name, Universal Book Reader is really a universal book reading application allowing you to read the eBooks from the convenience of your smartphones.
Okular - Okular is a universal document viewer based developed by KDE.
iReader - iReader is one of the most accomplished ways to read the books right from your smartphones.