Place Value Cups. Use the cups to understand place value practice counting forward and backward learn the names of large numbers decompose numbers to expanded form. I would either label the cups 'ones' 'tens' etc. or add a comma cup or decimal point cup
Measurement Inquiry - For CAP classrooms, this could double in the discovery center with a graph (children put their name under the color they think has the most)-- Use non-breakable PLASTIC jars and hot glue the lids on.