OpenStax
Open Stax: Anatomy & Physiology: The Pituitary Gland and Hypothalamus
Learn about the hormones released by the pituitary gland, their target cells, and their principal actions, as well as the structure and function of the hypothalamus.
Regents of the University of Michigan
Animal Diversity Web: Mammary Glands
A very solid history on the evolution of, and function of, the glands that give the group mammals their name. Good comparisons of other mammals and their function.