There are some fantastic resources available on the web for exploring Transpersonal Psychology and Holotropic Breathwork. The following is a shortlist of resources that will help you to start finding your way through the transpersonal landscape.
The adventure of self discovery by Stan Grof
When the impossible happens by Stan Grof
The Holotropic mind by Stan Grof
Thirst for Wholeness by Christina Grof
Grof Transpersonal Training
Stanislav Grof
The transpersonal vision - Youtube seminar by Stan Grof
Music for breathwork