"Show What You Know" board.(I blow this size up using a poster maker at work.)
Use as an exit slip for any subject or any grade level.. Ask the students a question...Example- "What is 4x9?" Have the students answer the question on a post-it and then as they leave the room or have finished answering, have the students place their post-it on their assigned number.
This is an easy way to see which students still need help and which students understand.