We use letter cards and number cards similar to these but I needed more for our calendar routine. Previous to this, they have been using a shape.
The child will say the name of the shape and then a sentence such as: A chip can be a triangle. A sign can be a triangle. Pizza can be a triangle.
In addition to these shape cards, I have also created some color cards to compliment these shape cards. They have a color, name, and a few items that are that color.
You can see what our board looks like here: