ArcGIS Online continues to be improved, with additional functionality and data added. With tools to import shapefiles, text data, gps files, or KML data, it eliminates the need for a local ArcGIS installation (in some cases).

See http://www.esri.com/news/arcwatch/1211/new-content-basemaps-and-tools-added-to-arcgis-online.html

or http://blogs.esri.com/esri/arcgis/2011/10/12/new-arcgis-online-basemaps/

or http://www.esri.com/news/arcnews/fall11articles/arcgis-online-whats-new.html for more information about ArcGIS Online.