ArcGIS Explorer Online
With ArcGIS Explorer Online, you can easily explore, visualize, and share GIS information. Use it to directly access basemaps and other content. You can even use it to create an interactive slideshow.
ArcGIS Explorer is a free application that runs in a browser. It is built using Microsoft Silverlight.
Open ArcGIS Explorer Online
A more simplified user experience
Features can be dragged and dropped onto maps
Sharing information pop-ups and notes is easier. For example, you can make notes in a feature layer that can be shared across clients such as the ArcGIS.com map viewer and ArcGIS Explorer Desktop.
Presentations can be shared via direct URL access to the presentation of a map, making it much simpler to share your presentation with a user who has never used the application before. See an example.
Support for time-enabled web maps