Cheyenne Sun dance, c1909. Source: wiki.
Supplementing my series on Native American cultures (notably Navajo rituals and the Ghost dance), Sun dance rituals are still performed by many groups of Plains Indians of north America such as the Cree, Salteaux, Lakota, Dakota, Nakota, and Blackfoot. 
The Sun dance is a complex series of rituals for the healing of the community, with drumming and singing, held annually over many days and nights in late spring or early summer—and preparations are said to take up much of the year in between. Ritual practice varies between tribal groups, and over time.
A medicine lodge is constructed of pole rafters radiating from a sacred central pole. The arena is surrounded by a camp of kin and friends singing and praying in support of the performers. For young male dancers among some groups it is an ordeal, an extreme physical and spiritual sacrifice which they have vowed to endure both for their own merit and to ensure tribal well-being. Having fasted for many days in the open, as they dance around a central pole they perform self-mortification, the skin of their chests or back pierced with skewers tied to the central pole (for self-mortification rituals elsewhere, see Dervishes of Kurdistan, including Amdo Tibetans and Hokkien Chinese, and the Rufai sect in the Balkans). But this is far from standard today, and it doesn’t feature in some early accounts.
Shoshone Indians perform Sun dance at Fort Hall, 1925. Source: wiki.
Along with the whole suppression of indigenous peoples, the ritual was prohibited from 1883, but the ban was enforced only patchily. Detailed early studies include
- George Amos Dorsey, The Arapaho Sun Dance: The Ceremony of the Offerings Lodge (1903, 228 pages, lavishly illustrated)
- Clark Wissler, The Sundance of the Blackfoot people (1918).
The ban was lifted in Canada in 1951, in the USA in 1978. In 1993 a Lakota summit issued a declaration:
Whereas sacrilegious “sundances” for non-Indians are being conducted by charlatans and cult leaders who promote abominable and obscene imitations of our sacred Lakota sundance rites; […] We hereby and henceforth declare war against all persons who persist in exploiting, abusing, and misrepresenting the sacred traditions and spiritual practices of the Lakota, Dakota and Nakota people.
Non-indigenous people were banned from attending the ritual in 2003.
Part of a trilogy on on the lives of Kanai Nation Blood Indians of the Blackfoot confederacy in Western Alberta, the short film Circle of the Sun (1960) shows little of the ritual, but rather the changing tastes of young people no longer bound to the reservation (oil-rigging, rodeo):
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Zitkala-Sa, 1898 with violin. Wiki.
The Dakota activist Zitkala-Sa (1876–1938) chronicled her struggles with cultural identity; her training in WAM led to The Sun Dance opera (1913), with William F. Hanson. Here’s a documentary:
 Among many online resources, see e.g.
and the detailed account