This site, sponsored by Geology.Com, provides a list of erosion lesson plans, classroom activities, projects, and demonstrations.
http://geology.com/teacher/erosion.shtml
This lesson, sponsored by Discovery Education, provides a lesson on desertification suitable for grades 9-12.
http://school.discoveryeducation.com/lessonplans/programs/desertdwellers/
This site, sponsored by Nova Online, presents information about the Arabian Desert with connections to teacher activities and desert-related links.
http://www.pbs.org/wgbh/nova/ubar/hotscienceubar/desert10.html
This site, sponsored by How Stuff Works, presents an easily understandable discussion of sand dune formation.
http://geography.howstuffworks.com/terms-and-associations/sand-dune1.htm