An alternative to the page-chapter-paragraph documentation approach. LivCos allows you to teach the computer the structure of your content, so it can support you in various contexts. Pages will be generated as one of many views on the actual content.
Metaquokka is a highly configurable xml editor, currently available as Gridsphere portlet. Besides the default format, there is suppoert for ESysXML, a simulation description scheme for a geodynamics framework. Supports Generic Mapping Tools rudimentary.