To throw my hat in the ring, these are the places I'm aware of (in no particular order):
1) Performance Freediving
http://www.performancefreediving.com/
They have courses on the West Coast, Florida and Hawaii scheduled
2) Check you local YMCA, they might have an intro course
3) IAFD USA (International Association of Free Divers)
http://www.iafdusa.com/coursdr.htm
They have a couple Constant Ballast Courses coming up
4) Dive Tech in the Cayman Islands
http://www.divetech.com/
They have a long list of courses available. Looks like they are on demand as opposed to scheduled
5) A friend of mine, Trace Malinowski developed and teaches a course for PDIC on the east coast/Pennsylvania area.
http://hometown.aol.com/tracemalin/index.html
Then you have the occasional courses taught by Tanya Streeter, Pipin, Loic LeFerme etc..
Hope this helps. (and I hope I spelled everyone's name correctly)
