WinDjView - WinDjView is a fast, compact and powerful DjVu viewer for Windows with tabbed interface, continuous...
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
DjVuLibre - DjVuLibre: Open Source DjVu library and viewer
calibre - Ebook manager, viewer & converter
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
Okular - Okular is a universal document viewer based developed by KDE.