Turtle Geometry For Primary and Elementary Classrooms is directed at Montessori (mainly elementary) teachers, but others might find it interesting. You can find good background information on the Montessori method through the Montessori links at left.
Binomial Square Explained. This paper explains the math behind the pattern found on the top of Montessori's binomial cube box.
Lateral Area of a Cone Revisited. Some thoughts on deriving the formula for the lateral area of a cone.
Signed Number Stuff. Notes from some work I did on positive and negative numbers with kids at the Center for Talent Development, including lots of word problems. These kids were in fourth, fifth and sixth grade but tested a couple of years ahead in math. Given the background that Montessori kids get in elementary, the word problems might be useful as written or adaptable for use in Montessori classrooms.
Variation on Conversion from Base 10. A lesson that might be used before introducing to children to conversion of numbers from base 10 into other systems before introducing them to the paper and pencil algorithm.