Wikipedia: Blackfoot Language - Article including a phonological inventory and orthography. - http://en.wikipedia.org/wiki/Blackfoot_language
The Blackfoot Language - Information on the dialects, writing systems, and sociolinguistics of Blackfoot, from linguist Don Frantz. - http://people.uleth.ca/~frantz/blkft.html
The Linguistic History of Blackfoot - Discussion of the historical relationship between Blackfoot and other Algonquian languages, and a look at the evolution of Blackfoot grammar. - http://people.uleth.ca/~frantz/blhist.html
Kids' Stop Languages: Siksika - Audio phrasebook in Siksika Blackfoot, aimed at children. - http://www.ainc-inac.gc.ca/ks/5080_e.html
Blackfoot - Blackfoot linguistics information and Blackfoot-language texts. - http://www.fp.ucalgary.ca/howed/blackfoot.htm