1. http://picasa.google.com. http://picasa.google.com.
2. http://www.waze.com. http://www.waze.com.
3. http://www.openstreetmap.org/. http://www.openstreetmap.org/.
4. http://snap.stanford.edu/data/loc-gowalla.html. http://snap.stanford.edu/data/loc-gowalla.html.
5. http://crowdflower.com/. http://crowdflower.com/.