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
(can use the same idea to show multiple ways of adding/subtracting) GREAT!-- multiplication unit to teach repeated addition, groups of, commutative property, and arrays. You could also replace one with a multiplication word problem and picture.