If you have a kid learning to count to one hundred who enjoys playing with numbers and patterns, this is a great lab to reinforce those skills. You can easily print out or even buy a hundreds chart (we had one hung in our bathroom for several years!). But it is even cooler to make your own.
And anything done on a huge scale is immediately more engaging.
For our hundreds chart we used a big piece of free cardboard I picked up from Sam's. I am in the habit of always grabbing a sheet when I am there as they have unlimited uses around here.
Then with markers, crayons or paints, make a grid and invite your kid to fill it in. They will quickly begin seeing patterns in all directions.
When you are done hang it up or keep it handy. My son loves to look at this and refers to it when adding up big numbers.
If you have older kids, you can adapt this to make a multiplication chart!