Counting is a great math readiness skill. You can use this free Pink Tower and Counting Printout to teach counting and number recognition. This lesson is an adaptation of the Montessori pink tower.
First sort the cards from smallest to largest, count the cards from one to ten, and finally teach the number symbols using the 3 period lesson. For younger children use the first three cards and add more gradually.
Check out montessorimom.com for more free printouts and lessons.