TargetMap is an online mapping tool based on Google Technology. You can create all kind of maps by simply uploading your data fro man Excel Sheet.
All posted maps are accessible from TargetMap’s home page. For example, one of the leading maps currently is a map of changes in radiation in Japan after the Fukushima nuclear plant incident. You can search for maps by keywords or browse by category.
The catch on the free version is that you have to be willing to share your data and maps publicly. There is a premium version available for $195/year that allows the maps to be stored privately.
However, you can look at all kinds of maps that are available. Here are some examples:
Happiness Map: http://www.targetmap.com/viewer.aspx?reportId=2903
Cellular Phone Penetration in Africa: http://www.targetmap.com/viewer.aspx?reportId=4760