Sigil - Sigil is a multi-platform WYSIWYG ebook editor. It is designed to edit books in ePub format.
calibre - Ebook manager, viewer & converter
Vellum - Free beautiful hand-curated wallpapers for the iPhone
Pressbooks - Create books: print and ebooks
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Visual Paradigm - Looking for an affordable software with Enterprise Architecture tool, PMBOK tool, UML tool, Agile tool, BPMN tool and UX tool? Read this page for details.