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
Area/Perimeter robots - get the children to draw robots and write the area and perimeter of each section (Sally Maddison) To take it a step further, have middle school students create a small robot and then enlarge it proportionally!