American Montessori Society, http://www.amshq.org/ 

Montessori Materials, http://www.montessorimaterials.org/ 

North American Montessori Teachers' Association, http://www.montessori-namta.org/ 

The International Montessori Index, http://www.montessori.edu/

The Montessori Foundation, http://montessori.org/ 

The Montessori Method

Michael Olaf.  Link to articles, books and materials.  http://www.michaelolaf.net/