For Cohen's birthday, his Aunt gave him a set of Unifix Cubes. I had heard of these before, but I had never actually seen them in action. These cubes are 1 inch square, and they come in all colors. We are currently using them to learn to count, recognize colors, sort colors, and they are also useful for teaching addition/subtraction/multiplication/division, but we are no where near that in our PreK3 curriculum. Maybe he'll learn that next year [sarcasm]. We will use them later this year to learn patterns, grouping, and measurment (largest/smallest).
Anyway, here are a couple pictures of Cohen playing with his Unifix Cubes. In this exercise, he was instructed to put a yellow block on top of a blue block (we are working on counting - 2 blocks - and working on understanding top/bottom). This also works on motor skills, because he has to actually put the blocks together.
If you have a child, you need these! Cohen's Aunt also got him a workbook that goes with it to help him learn. It is a very useful tool to have and it gives great ideas for other learning exercises. There are fun workbooks for kids of all ages, and it's a great hands on, visual learning tool.