The Center for Urban Pedagogy: an NYC based non-profit that uses art and design to enhance civic engagement. They are pros at making complex policy and planning issues more accessible to the general public, and in a way that is strategic for community organizing goals. See especially their Making Policy Public and Envisioning Development series for group project ideas.
Hester Street Collaborative: another super cool NYC non-profit that uses art and design for social change, in collaboration with community groups and students.
Dr. Pop: a popular education website that helps people become better story-tellers and strategic thinkers; Dr. Pop tells complicated stories in simple ways, through games, videos, and other media, and then explains how to do it.