The American Academy of Dermatology has a great site for kids devoted to skin, nails, hair and other interesting dermatology-related topics. This site covers all those topics you had no information for such as birthmarks, itching, scars, and more.
Skin — it's all over you! — Great instructional page from the Women's and Children's Health Network about skin that you can share on your interactive whiteboard. All about skin parts and purpose. Includes some great activities you can do with your class.
Skin Lesson Plans
Lesson plans on Sun Safety from U. S. Department of Health.