Our GCA curriculum comes with tons of math manipulatives. The girls love playing with these and frequently pull them out on their own. The most favorite of those math manipulatives is what I call the "plastic shapes." The girls will spend hours at their desks making designs and pictures out of the shapes:
It may be hard to tell, but the girls made a checkerboard, a rocket, and a few other designs.
I have also bought some patterns which the girls like to use with these plastic shapes. But, I also like the creativity free play with the shapes encourages.