Substance is an open-source web-based document authoring and publishing platform.
"Document authoring used to take place in word processors on the Desktop like MS Word or Open Office. We believe that today this can all be be done in the browser, in a simpler, more collaborative way."
Semantic Editing
Unlike traditional word-processors, Substance focuses on content, by leaving the layout part to the system, not the user. Because of the absence of formatting utilities, it suggests structured, content-oriented writing.
Collaboration
Substance targets open collaboration. Readers can participate and comment on certain text passages. In future they'll even be able to submit patches, that can be applied by the owner.
Integration
Substance exposes documents as data, ready to be compiled into arbitrary output formats (HTML, PDF, ePub, ...) or integrated with other applications (like websites).
In addition Substance.io can export to major publishing formats including PDF, ODT, ePub, and others.
Find out more: http://substance.io/
Getting Started: http://substance.io/substance/substance
Use Substance as a Blog Engine: http://substance.io/#substance/substance-as-a-blog-engine