Mayo Clinic
Mayo Clinic: Vitamin and Mineral Supplements
This site from the MayoClinic.com contains an article entitled, "Using vitamin and mineral supplements wisely". Focuses on the right balance of minerals and vitamins, but shows the benefits of whole foods as well.
Other
Doctor Yourself: What's the Difference Between Natural and Synthetic Vitamins?
Discusses the non-nutritional ingredients in vitamins and explains the differences between natural and synthetic vitamins. The examples of vitamins C and D are looked at in more detail.