I started using StreetComplete after @aperezdc mentioned it. You can help fill in OpenStreetMap data by answering simple questions about your surroundings. It’s a fun thing to do while you’re waiting for a bus or you’re in the queue for a bubble tea. https://play.google.com/store/apps/details?id=de.westnordost.streetcomplete
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!