Results not only show examples of how to technically build GIS applications enabling user collection and interaction with geospatial data, but they also draw conclusions about the methods and needs of public participation. We describe three projects with different scales and purposes in the context of urban monitoring and planning, and tourism valorisation. In each case, an open source architecture is used, allowing users to exploit their mobile devices to collect georeferenced information. This data is then made publicly available on specific Web viewers. Analysis of user involvement in these projects provides insights related to participation patterns which suggests some generalized conclusions.