I gave each student a "checker board" that I'd created and run off on colored tag (then laminated). Each table got their own set of math manipulatives: buttons, pom-poms, colored blocks, unifix cubes, and bears. All they had to do was put one object on each square. At first, they used all the colors, so I made them clear their boards, and do it again, but using only one color. (These pictures are from when they had done the activity a second time, using a single color.)
To extend the lesson, I ask them to put 2 items on each square. Then 3. I stop at 5 because the squares tend to get too crowded. For the blocks, I let them "build" a small tower on each square. (They love doing that.) The next time they do this lesson, I give each table a different set of manipulatives.