Stanford Participatory Budgeting Platform allows cities, municipalities, states and foundations and other organizations to run a participatory budgeting (PB) election in which people can vote on the budget. The project is open-source and free. The platform has been used in many cities in the United States, such as Chicago, Seattle, Boston, and New York City.
Synapp is a project focused on connecting communities through collaboration and decision-making. It's premise is that one can facilitate large-scale deliberation through simple and intelligently chosen tasks. For an example of crowdsourcing laws using Synapp, see our article on Finland's off-road traffic law.