This address: esriurl.com/ago5x5
Easy "first time intro" to ArcGIS Online in a hands-on fashion: Five things you can do with ArcGIS Online, each in about five minutes. Good for schools. Afterwards, explore the rest of the "Getting Started for Educators" document, where this doc is Link #6 of 25.
(As of July 2021, the PDF includes latest versions for both the new Map Viewer and Map Viewer Classic.)
(As of Sept 2022, the new Map Viewer version also points to a StoryMap version with embedded videos and interactive maps.)
(Updated as of Sept 12, 2022)
