Homeschool activities has an idea of how to use fallen leaves to make a craft project tree just add glue.
Good for ages 4 and up.
Get the instructions here:
http://www.homeschool-activities.com/fall-crafts-for-kids.html
Preparing your child for preschool uses colorful leaves with a large green leaf as the backdrop for the treetop.
Get the instructions here:
http://preparingyourchildforpreschool.com/blog2/2010/11/15/easy-crafts-for-kids-tree-with-real-leaves/