Tray activities are out on a shelf in our school room and open for the kids to use as freely as they want.
This first one is so simple but I loved the metal cups(business Costco but I've seen them at wal-mart too). They make a really nice clinking noise as they take them off of the stack. The glass gems(dollarstore) are together in a plastic bowl.
The idea is to have the child unstack the cups and put 1 gem in each of the 10 cups. This teaches one to one correspondence and problem solving skills(in the picture Drake realized that he didn't have a gem for the last cup so he started to look in other cups and found that he had put 2 in another cup).
This next activity is just little rings in a cardboard jewelry box. Open and close plus it is just pleasant to touch the tiny rings. Bonus(that I didn't plan) is the child can sort the colors.
This last one is nuts and bolts from the hardware store mixed with a set from the target dollar spot. I loved how contrasted the colors, textures and weights were! The kids really liked all of these activities:)