When we are in our geometry unit, I like to give students tangram challenges. Laura Candler has a wonderful Tangram Polygon Explorations that I give to my kiddos. I use it as a center to go to once they have finished their work. Their are a few different activities in her packet, so it can keep them busy for days. It is a free activity on TPT, so I'd really recommend you check it out!
What are your favorite math manipulatives and activities to do with them?