This address: esriurl.com/agoskillbuilder
The ArcGIS Online SkillBuilder is a "quick and dirty" tutorial for working with ArcGIS Online as a teacher or as a K12 student. Each page has 4-6 rows representing steps in learning about the software, with a thumbnail showing the item or process, a couple of sentences to read, and something to click and do. Designed for teachers to feel comfortable presenting to middle school students or above.
Updated 4/26/2021 with info about new Map Viewer and Classic Map Viewer.
Updated 7/03/2022 with current links and info.