operability, maps overlaid on Google Maps and travel business, travel planning... Places interesting for tourism and sightseeing

These following web services are good examples of interoperability of geo-data.


Example of an overlaid on google maps based on crowdsourcing the number of geotagged Panoramio photos (owned by Google in July 2007).
http://www.panoramio.com

Example of a heatmap overlaid on Google Maps, based on crowdsourcing (the number of Panoramio photos taken at each place in the world).

http://www.sightsmap.com/

and if you click on "see more"

You will get 5 buttons:
panoramio, google streetview, wikipedia, tripadvisor research, and google search.