Three year olds get to work on patterns and colors and matching. A lot. Here's another activity for preschool that qualifies for all three.
I inherited hundreds of these inch blocks. I used them often when I taught 2 and 3rd grade. We used them for making patterns, introduction to measuring, working on perimeter and area, etc. They are pretty open ended. To make the pattern cards, I cut out inch pieces out of construction paper and glued them on 3 inch strips. Then I laminate everything of course. I'm taking them to the nature center today for my early arrival kids to try out.