...using square tiles. Have students create rectangles with different dimensions, (3 x 5, 2 x 7, etc.) and have them find the perimeter. Then challenge them by giving them the perimeter and having them find the dimensions. You can even tie in area. Students can copy they're rectangles on graph paper.
Another activity could be with toothpicks. Have students create different shapes and find the perimeter with the toothpick being one unit.
Hope this helps!
