Unifix Cubes are large, colorful plastic cubes that snap together. They are useful manipulatives for preschool through second or third grade. Hands-on demonstrations using these snap-together blocks can be extremely helpful in teaching concepts to your children, even if you are using a curriculum. The visual presentation and hands-on practice will help children to better understand what they are doing.
Didax sells various sets of Unifix Cubes. A set with 100 cubes should be sufficient for most situations. Developing Mathematics with Unifix is a useful book that shows how to teach kindergarten through third grade level concepts with Unifix. It includes reproducible pattern and activity sheets.