At what age did you introduce math lessons to your children? I'm interested to see what age is appropriate for my daughter (she's two going on three) to begin lessons in math.

Doesn't have to be formal! You can start at that age already - teach addition at the supermarket (how many things are going into the cart), subtraction at the dinner table (how many pieces of broccoli left after she eats one or two), fractions through pizza!