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).
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/
The Life Resources Shop sells a wide range of English language NVC materials from its internet shop based in the UK. It also also sells NVC Dance Floor materials in English, Dutch, French, German and Swedish. Also gives contact information for the distributor of the NVC Dance Floors in Danish, and for North America and Australia distributors: http://www.life-resources-shop.com