Via the ArcGIS Online blog, details of the latest updates to ArcGIS Online, from Bern Szukalski...
New Enhancements in the ArcGIS.com Map Viewer
Improved support for adding shapefiles to a map
Measuring tool
Bookmarks
Publish web mapping applications
Customize web mapping applications
Save item properties
Additional support for KML
Disable pop-up windows on feature layers
New templates
Javascript and Flex mobile applications
ArcGIS Online for organizations - (Note: These capabilities are currently available only via a controlled early-adopter beta program. Later this fall these capabilities will be available to all ArcGIS 10.1 beta community participants.)
By acquiring an ArcGIS Online subscription account for your organization you can manage your users, create custom home pages, leverage Esri-hosted map services for quick and easy map publishing (without needing to manage your own ArcGIS services), and more.
See ArcGIS.com
For more on ArcGIS Online and updates be sure to follow @bernszukalski on Twitter
