Home page for Magento 2 preview documentation, featuring work in progress for beta developers’ release. Includes KB articles, sections of guides in progress, and links to sections of the documentation on https://wiki.magento.com.
Magento 2 Preview Documentation
Locations and formats vary.
Staged HTML (Internal)
Using Services to Provide Data for Layouts: http://10.249.151.84/ext-drafts/service-impl/
Magento 2 Product Doc on Public Wiki
These need to be vetted because some of the content has gone stale.