You'll find documentation at http://docs.exponentcms.org and the api documentation at http://api.exponentcms.org.
You'll find information about ExponentCMS at http://www.exponentcms.org and the forum at http://forums.exponentcms.org.
We maintain the list of project milestones and issues on Lighthouse at https://exponentcms.lighthouseapp.com/projects/61783-exponent-cms, but may migrate to using GitHub for issues and milestones.