About Montessori

http://www.montessoricandy.com/2010/10/montessori-materials-purpose_08.html

http://www.michaelolaf.net/
http://mariamontessori.com/mm/

Learning to Share
Everyone Should Learn Math the Montessori Way
The Silent Journey & Discovery – A Photo Essay (Experiencing a Montessori school)

Thoughts on elementary math

http://www.mathedpage.org/early-math/early.html

Some parts can be a chore to read, but the various games/fun activity suggestions and the summary is really good on elementary math education (imho).