directory -- Meditation Internet Resources
Numerous links on meditation - organizations, teachers & retreat centers.
http://www.holisticmed.com/www/meditation.html

directory -- Yoga Journal Directories
Broad site covering yoga teachers, teacher training, studios, retreats, associations, books, etc.
http://www.yogajournal.com/directory

directory -- YogaFinder
Broad site covering yoga teachers, classes, teacher training, events, etc. Calls itself "the largest yoga directory on the internet."
http://www.yogafinder.com

teacher directory -- Iyengar Yoga Teachers
Worldwide
http://www.bksiyengar.com/modules/Teacher/teacher.asp