Esri announced on Friday that they are lifting most of the usage restrictions on ArcGIS Online map services. As of February, ArcGIS Online base maps hosted by Esri will be freely available to all users, regardless of the use (commercial, non-profit, internal, external, etc.) The only restrictions will be on very high volume transactions of 50 million or more per year. While some of these services could be better, some have some really terrific cartography. I really like the World Topographic Map, particularly for communities that have contributed to the Community Maps Program. And I remain excited that Esri is supporting OpenStreetMap as a base map option.
ArcGIS Online is evolving into an increasingly useful service with not just base maps but also high quality, specialized data sets, such as the US National Wetlands Inventory or the US National Soil Survey Map. There is also the ability to embed the maps in personal web sites. The ArcGIS Online blog has a nice set of examples for how these capabilities can be applied to a number of different scenarios.