A large amount of free geodata used today is derived from non-profit projects, often based on citizens' initiatives and voluntary work, but sometimes also involving businesses, public authorities and research institutions.
A characteristic feature of many of these projects is so-called crowdsourcing, i.e. that important tasks, in particular data collection, depend on the participation of volunteers, e.g. via the Internet. Rarely are the works of individuals involved.
Global projects such as OpenStreetMap (the free world map), GADM (global administrative areas), Natural Earth (small-scale vector and raster data of the earth) and Geonames (geographical place names) deal with the provision of map data.
Under the term Citizen Science, scientific projects are carried out by interested laymen. Within the framework of Luftdaten.info, Openair.Cologne und OpenSenseMap, for example, air data (e.g. temperature, humidity, fine dust, nitrogen oxides) are collected with the help of simple sensors, evaluated and made publicly available. The project blitzortung.org uses receiving stations to locate lightning and thunderstorms worldwide in real time.
Many more examples of Citizen Science projects and crowdsourcing are listed in the Wiki of Forschungsdaten.org.