OpenStreetMap

OpenStreetMap (OSM) is a huge collaborative database of geographic information that anyone can use and edit (sort of like the Wikipedia of the map world). OpenStreetMap is run by a member-run non-profit foundation that is funded by members (individual and organisational) as well as donations.

Since OpenStreetMap is foremost a map database with very limited map-related services (routing, Points-of-Interest search, etc.), many free, open-source & privacy-preserving resources have been built on top of the freely licensed OSM data.