Egg Carton Flowers can create a colorful Card! Great spring activity for kids!
Last of the Autumn Leaves: Leaf mobiles/sun catchers (project page also shows some awesome suncatchers) This is just the idea I had.
hedgehog fall leaf craft - I did this with my son's class and it was a total hit. I'd recommend using leaves that aren't brown yet, as the brown leaves are more brittle and hard for kids it work with.