Sigil - Sigil is a multi-platform WYSIWYG ebook editor. It is designed to edit books in ePub format.
Vellum - Free beautiful hand-curated wallpapers for the iPhone
Jutoh - Epub editor, convertor and creator software for Mac and PC.
Papyrus Editor - Papyrus is a simple online editor to create ebooks.
calibre - Ebook manager, viewer & converter
Atticus - Create professional print books and eBooks easily with the all-in-one book writing software.