OpenStax
Open Stax: Anatomy & Physiology: Skeletal System Functions
This site helps you understand the human skeletal system, a body system composed of bones and cartilage that performs critical functions for the human body.
Other
Dr. Saul: Biology in Motion
This interactive site provides animations and activities in several areas of physiology. The images are simple, but clear. The accompanying text provides a good description of the process being shown.