Puddle Dancer Press (publishes many NVC materials): http://nonviolentcommunication.com/
NVC Dance Floors offer a way to learn, practise and teach NVC using spatial layouts that represent various NVC processes (eg transforming anger, self empathy, dialogue).
NVC Dance Floors and other materials are available from http://www.life-resources-shop.com
The Learner centered differentiation exercises are designed to help participants discover some of the core principles of NVC for themselves.
The Emotional Competency website helps people explore the logic of passion. See: http://www.emotionalcompetency.com/