For going deeper, including release notes / change lists for versions of Omeka code, software developer supportive explanations of structures, functions, and how to hook into, theme, or otherwise "tweak" the system at a code level.
Homepage for documentation for the Omeka project, with links to topics such as:Getting Started with the Software Application
Getting Started with Project Planning
Working with Omeka Admin
Working with Omeka Plugins
Designing & Developing with…