On-Line Biology Book: The Integumentary System
Offers an introduction to the skin's follicles and glands and sensory reception as well as its selective permeability.
www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookINTEGUSYS.html
Blue Histology: Integumentary System
Provides an introduction to the skin and its appendages.
www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm