** Always remember to save! **
Overview and using Omeka by Laurie Allen, a Penn librarian. The "Getting Started with Omeka" tab is a good primer when you're first starting out: https://guides.library.upenn.edu/omeka
The forum is a very good place to look to problem solve. Do make sure to pay attention to dates of the questions and responses or the version discussed. Omeka gets updated frequently and workarounds or remedies may no longer work for the version you're using.
J.F. Leddy of the University of Windsor, Ontario
I found the Building a Neatline Map video to be incredibly useful when starting out. I'm more of a visual learner, so watching him go through each of the steps helped me understand exactly what I was meant to be doing. The Item Type Metadata video is also of potential use.
I didn't end up using georectified maps, but I think this tutorial could be quite useful, if historical maps are to be used a basemap.