Recently ArcGIS.com went live as a public beta, and along with that ArcGIS Explorer Online also went into public beta. You can start ArcGIS Explorer Online by visiting ArcGIS.com and clicking Start ArcGIS Explorer Online or by going directly to explorer.arcgis.com.
ArcGIS Explorer Online is similar in appearance to the desktop version of ArcGIS Explorer, and has some of the same capabilities, but it’s a lighter weight version that works in a browser, and is built using Microsoft Silverlight.
We’ll stay focused on ArcGIS Explorer desktop here on this blog, and will cross reference where appropriate. For more details on ArcGIS Explorer Online, stay tuned to the ArcGIS Online blog.