Circadian Rhythm (Wikipedia)
This extensive dictionary definition from the most popular on-line encyclopedia gives those with little knowledge about circadian rhythms an overview of the topic.

Circadian Clocks Web Course · Video
This site offers a series of lectures in the form of a course on circadian clocks (in the Coursera system). The instructors are Dr. Martha Merrow and Prof. Till Roenneberg from Ludwig Maximilians Universität München.

Circadian Rhythms (Kimball's textbook)
This page correponds to the section on circadian rhythms in John W. Kimball's textbook Biology (6th Edition, Wm. C. Brown).

The Brain, Circadian Rhythms, and Clock Genes
This article by Dr. Michael Hastings includes diagrams and explanations of circadian clock molecules in flies and mammals.

Sleepless at Stanford
This article by Dr. William Dement discusses the need for adequate sleep and its connection with the biological clock.

The Mammalian Biological Clock · Video
This animation on the Howard Hughes Medical Institute's Biointeractive site describes the molecular mechanism of the circadian clock in mammalian cells.

Circadian Rhythms: Organism, Cell, Genes · Video
This 20-minute video is an elegant lecture by Dr. Joseph Takahashi summarizing research on circadian rhythms from organisms to cells and to genes.

Clocks and Rhythms: Interviews · Video
This page contains links to numerous videos of interviews with biological rhythm researchers who attended the 72nd Cold Spring Harbor Symposium on Quantitative Biology in 2007.

Center for Biological Clocks Research (Texas A&M U.)

Center for Circadian Biology (UCSD)

Sleep Chronobiology Group (University of Surrey)

Center for Human Sleep Research (Stanford University)

Center for Sleep & Circadian Biology (Northwestern U.)

Rhythms Research Group (Michigan State University)

Swiss Center for Chronobiology (University of Basel)

Circadian Lighting Association

European Biological Rhythms Society

International Society for Chronobiology

Japanese Society for Chronobiology

Society for Light Treatment and Biological Rhythms

Society for Research on Biological Rhythms

Chronobiology International (Taylor & Francis)

Biological Rhythm Research (Taylor & Francis)

Journal of Biological Rhythms (Sage Publications)

Journal of Circadian Rhythms (Ubiquity Press)

Sleep and Biological Rhythms (Wiley)

Circadian Technologies Inc.
This site is the homepage for Circadian Technologies Inc., a research and consulting firm that assists managers of shift work operations.

Shiftwork Solutions LLC
This is the homepage for Shiftwork Solutions LLC, a company that provides assistance to shift-workers to help them manage their workload fluctuations with the goal of lowering costs and improving productivity.

Jet Lag
This European site describes the causes of jet lag and provides several options for preventing it.

Tuck
This site provides advice about sleep disorders with special emphasis on the choice of mattresses.

Mount Sinai Sleep Disorders Program
This section of the Mount Sinai Medical Center in New York City describes sleep disorders and tests that can be conducted at a sleep clinic.

Sleeplessness and Circadian Rhythm Disorder
This article from Medscape indicates that behavioral modification is helpful in patients with irregular sleep-wake cycles.

Circadian Biology and Clinical Medicine · Video
This video is a lecture by Dr. Charles Czeisler (Harvard Medical School) on "Application of Sleep Science and Circadian Biology to Clinical Medicine".

Sleep Disorders and Health
This site provides a non-technical description of health problems associated with sleep disorders.

Carl Johnson's Laboratory
The web site of Dr. Carl Johnson at Vanderbilt University (Cellular, molecular and evolutionary analyses of biological clocks).

Andrew Millar's Laboratory
The web site of Dr. Andrew Millar at the University of Warwick (Biological clocks in plants).

Choogon Lee's Laboratory
The web site of Dr. Choogon Lee at Florida State University (Molecular mechanism of mammalian circadian rhythms).

Chris Colwell's Laboratory
The web site of Dr. Christopher Colwell at the University of California, Los Angeles (Molecular, cellular, and systems-level mechanisms of circadian-rhythm generation).

Martha Gillette's Laboratory
The web site of Dr. Martha Gillette at the University of Illinois, Urbana-Champaign (Neuroscience of circadian rhythms).

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