Spyder is having great fun with pentominoes lately.
He's been playing online at Scholastic's Chasing Vermeer website, but he wanted his own set. I haven't been able to find a decent set locally, and he's impatient (like me!) so he made his own.
He used a gift box from Christmas for the card stock and did all of the measuring and cutting by himself, using these instructions from his Chasing Vermeer book. (FYI: the link to the instructions is in PDF format.)
He's been carrying them around in his pockets, taking them out to make squares and rectangles and pictures. And I admit, it's a little bit amusing to hear him have a math conversation with other children without realizing what he's doing. He's become a vocal "I hate math!" person lately, and he has no idea that he's spending most of his free time playing with math.
Next up: making a 3D set with wooden blocks.