Mini - Table Saw / Router / Shaper for Dremel rotary tool. Now that the Dremel contest voting is over I guess it's ok to update this instructable. Here is a "supplement" video showing the table saw extension in action.
Growing bean plants in CD cases so all the parts can be seen. Have kids write about their finding and act out/ put together a dance describing the life cycle from seed to plant (Movement, writing, science)
Balloon ninjas to shoot with nerf guns. This is a fantastic idea! Great for little boys! I know this was posted as an idea for little boys. but I think I'd like to have a nerf gun battle with these ninjas.