http://www.nais.org/about/article.cfm?ItemNumber=145556

The National Association for Independent Schools (NAIS) website has this posting written by Wendy Carlise.  She defines Montessori not as a “teaching method” but rather more holistically as ”the development of the human being to its fullest potential.”  I think this article really explains Montessori well, as opposed to just giving it a technical definition.