We have an estimation jar activity that we do daily as part of our calendar activities. We use an assortment of large, multi-shaped, colored buttons. We work on estimating strategies. The children have a variety of objects to estimate at the math center. They can practice these estimating strategies with a variety of collections.
I created estimation recording printables that students use to record their estimates or guesses, along with a small poster that is posted in the math center with the counting jar.
Download them HERE.