The Holotropic Breathwork community is international in scope with a professional association and training program.
The Association for Holotropic Breathwork International has a great site that is open to the public. ABHI's mission is to support the practice of Holotropic Breathwork as a resource for healing and transformation.
Go to www.ahbi.org to encounter the many interesting people and discussions that make up this community. You can watch video's of Stan and Christina Grof who founded this work. There is a Mandala Gallery where the drawings that emerge after breathwork are posted. Post your own! ABHI wants everyone who cares about Holotropic Breathwork to get involved. Sign-up is free of charge. See you there!
The Grof Transpersonal Training site has a good introduction to Holotropic Breathwork as well as the training that facilitators undergo. Some of the educational modules are open to the public while others are only for those intending to become certified facilitators. There is also a bookstore with all of the Grof's books as well as many other resources that are about or relevant to breathwork.
Holotropic breathwork even has a wikipedia entry.
Finally to get an overview of the depth and breadth of Stan Grof's lifetime achievements the speeches made as he is granted and accepts the VISION 97 Havel Award are good reading.