PBS
Pbs: Frontline: Dreams of Tibet: Buddhism
An excerpt from Trespassers on the Roof of the World discusses the spread of Buddhism to Tibet and the origin of some of the unique practices of Buddhism seen in Tibet, such as rule by lamas and the prayer-wheel, or mani-chuskor.
Wikimedia
Wikipedia: Tibetan Buddhism
Encyclopedia entry for Tibetan Buddhism, also called Lamaism, from the openly editable online encyclopedia Wikipedia.
University of Missouri
Museum of Anthropology: Minigalleries: Symbols of Tibetan Buddhism
Examples of ritual and spiritual objects common to the practice of Buddhism in Tibet, including the prayer wheel.