Here are some suggestions for Catholic books for graduates: http://www.catholicfamilycelebrations.com/graduation.html
I'd love to have a non-Catholic option, too, besides "All the Places You'll Go" by Dr. Seuss. There is a whole display at Barnes and Noble for Books for Graduates. I'd love to find a book that doesn't appear "Religious" but can truly have a life-changing message. Any suggestions?