CartsPDX is a free iPhone application that lets users find food carts near their current location. If they wish to edit the details of a food cart (location, hours of operation, menu, etc) they can do so from inside the application. All data, including changes made by the user, are stored publicly on PDXAPI. Changes made by any user will show up for all other users, much like a wiki.
This application tries to embody the idea of the 'Civic web', a web in which you can more efficiently interact with your neighborhood. All data collected by the application and source code is 100% open source, which means that anyone else who wants to utilize food cart information can do so without my permission.