The Association on American Indian Affairs’ Dakota Language Preservation program on the Traverse Lake Indian Reservation has a rich website for Dakotah language learners. Resources include language games, a discussion forum, books, songs, art, and much more. Many resources are free; some are for sale.
Explore the website at http://aaialanguageprogram.org
Read a review of this website at http://falmouthinstitute.com/language/2013/01/learn-dakota-with-great-website