WebMD
Web Md: Depression Guide
This site from WebMD Health provides great information on depression. Includes a section on the facts of depression, types of depression, causes, diagnosis, treatment options, care giving, and different populations information.
Other
Sunnex: The History of Light Therapy
Contains a brief history of the use of light to treat Seasonal Affective Disorder. Includes information about case studies, time periods, and reliability.
The National Alliance on Mental Illness
National Alliance on Mental Illness: Depression
This site is a concise page from NAMI describing depression, its causes and symptoms, statistics, treatment, and more.