Ethnologue: Cheyenne - Basic demographic and linguistic information. - http://www.ethnologue.com/show_language.asp?code=chy
Wikipedia: Cheyenne Language - Article including a phonological inventory and some grammatical information. - http://en.wikipedia.org/wiki/Cheyenne_language
Omniglot: Cheyenne (Tsêhést) - The Cheyenne writing system (standard orthography). - http://www.omniglot.com/writing/cheyenne.htm
Cheyenne Language Surviving - Article about Cheyenne language preservation efforts. - http://www.turtletrack.org/Issues01/Co11032001/CO_11032001_Cheyenne_Language.htm