Help to improve the OpenStreetMap with StreetComplete!
This app finds incomplete and extendable data in your vicinity and displays it on a map as markers. Each of those is solvable by answering a simple question to complete the info on site.
The info you enter is then directly added to the OpenStreetMap in your name, without the need to use another editor.
I asked the developer Tobias Zwick the exact same question. His reply (in german, can anyone summarize it in english?):
I thought it was awesome he took the time to answer in such detail and startet support him on liberapay: Tobias Zwick