The ArcGIS Online website has the latest functionality and enhancements. For this reason, the What's new help topic only contains information about the latest update. But for those who want a quick reminder of what we released when, here's an archive of past announcements. For fun, we've included a 2009 video showing the original ArcGIS Online website. Enjoy.
Previous what's new announcements
A Look Back at the 2009 ArcGIS Online Website
In 2009 ArcGIS Online expanded from a map library to a website for sharing and collaboration. Step into the Esri Holistic Lab circa 2009 for a demo of the original ArcGIS Online website.