This document summarizes 20 existing co-creation platforms. It describes different types of co-creation such as clubs of experts, crowds of people, coalitions of parties, and communities of kindred spirits. Key principles of successful co-creation are inspiring participation, selecting the best ideas and people, connecting creative minds, sharing results, and continuing development. Platforms are compared based on parameters like number of people involved, frequency of interaction, competition level, project duration, and return for participants. The goal is to learn from existing examples of co-creation between industries, governments, and consumers.