Sleep is a natural state of bodily rest observed throughout the animal kingdom. It is common to all mammals and birds, and is also seen in many reptiles, amphibians and fish. In humans, other mammals, and a substantial majority of other animals which have been studied — such as fish, birds, ants, and fruit-flies — regular sleep is essential for survival. However, its purposes are only partly clear and are the subject of intense research.
Wikipedia article on the sleep, stages of sleep,sleep timing,functions,dreaming, effects of food and drink on sleep,anthropology,common sleeping positions, practices, and rituals, and other resources.
WIkipedia Article about sleep disorders,(somnipathy) , which includes a list of the various types such as Narcolepsy, Sleep paralysis,Restless legs syndrome and Sleepwalking.
Sleep Disorders Information, types of disorders like sleep apnea,sleep deprivation,insomnia, and more. Information about sleep disorders in infants and children, a sleep disorder forum, and a sleep test you can take.
Polyphasic Sleep: Facts and Myths
Comparing polyphasic sleep to regular monophasic sleep, biphasic sleep, free-running sleep, Uberman's Sleep Schedule and more about this unique sleep pattern.
National Sleep Foundation
Nonprofit organization supporting public education, sleep-related research, and advocacy related to sleep deprivation, sleep disorders, and more.
Sleep for Kids - Teaching Kids the Importance of Sleep
Learn about what happens while we sleep, play fun games, and keep a sleep record . Explains about dreams, and why sleep is important.
Uberman's sleep schedule
The Amazing Mind Blog - Six Incredibly Awesome Mind States You Can Experience
Wikipedia article about lucid dreaming. A lucid dream is a dream in which the person is aware that he or she is dreaming while the dream is in progress, also known as a conscious dream.
Rapid eye movement (REM sleep)
Short Wikipedia Article on Rapid eye movement Sleep, what occurs during REM, theories and fuctions, REM sleep in other animals, and more.
See also: Dreams and Visions