I recently started picking up a kindergarten math group. We've been practicing decomposing numbers. I will tell you that the Target Dollar Spot erasers make awesome seasonal manipulatives!
This drawer organizer from Target (in the kitchen area) is perfect for storing erasers at work stations or at small group.
These mats only have the number at the top. I laminated them, and then students can practicing decomposing numbers and write the numbers in the box.