Laughter Yoga in Dallas, Texas. Doctor says it reduces blood pressure and is a powerful therapy.
http://www.youtube.com/watch?v=DigAEY10gw0
http://www.youtube.com/watch?v=g8Pfa_YaOY8
http://www.youtube.com/watch?v=qrcZXGqUVrk
http://www.youtube.com/watch?v=pCrcFcfp-Mg