National Association of Holistic Aromatherapists 
This organization is an educational, nonprofit agency dedicated to enhancing public awareness of the benefits of true aromatherapy  and promoting academic standards in aromatherapy education and practice.
Aromatherapy Registration Council 
This website gives information on the registration examination for aromatherapists and provides a register of qualified aromatherapists.
International Council for Aromatic and Medicinal Plant  (ICMAP)
The Council's objective is to promote international understanding and cooperation between national and international organizations on the role of medicinal and aromatic plants in science, medicine and industry, and to improve the exchange of information between them.
Here are some good, reliable books:
Battaglia, S., (2003). The complete guide to aromatherapy. Brisbane, Queensland, Australia: The International Centre of Aromatherapy.
Bowles, E., (2003). The A to Z of essential oils. London: Quarto Inc.
Buckle, J. (2003). Clinical aromatherapy: Essential oils in practice, 2nd Ed. Edinburgh: Churchill Livingstone.
England, A. (2000). Aromatherapy and massage for mother and baby. Rochester, Vermont: Healing Arts Press.
Mojay, Gabriel (2000). Aromatherapy for healing the Spirit. Healing Arts Press.
Price, Shirley (1991). Aromatherapy for common ailments. Gaia Books.
Price, S. & Price, L. (2007). Aromatherapy for health professionals, 3rd Ed. Philadelphia: Churchill Livingstone Elsevier.
Schnaubelt, Kurt (1998). Advanced aromatherapy. Healing Arts Press.
Tisserand, Maggie (1996). Aromatherapy for women. Healing Arts Press.
Wildwood, Chrissie (1996). The encyclopedia of aromatherapy. Healing Arts Press.
Worwood, V. (1996) The fragrant mind. Novato, CA: New World Library.
Worwood, V. (1991). The complete book of essential oils & aromatherapy. Novato, CA: New World Library.