State historical societies and state archives often have extensive collections of materials regarding the Indian tribes that lived in their areas.  This may be true even if a particular group was located elsewhere.  The following are a few examples.

 Kansas Historical Society, Topeka  The Kansas society's website has a number of resources on American Indians, including several historic sites related to tribes that now have their heeadquarters in Oklahoma. 

Harvard Project on American Indian Economic Development

Harvard University Native American Program (HUNAP)

Indiana University, American Indian Studies Research Institute

ETC

A Guide to Native American Studies Programs
in the United States and Canada     
Robert M. Nelson, Editor.  Association for the Study of American Indian Literatures.  Revised Oct. 20, 2011.

A guide by region and state with information on many of the programs in the U.S. and Canada, and links to their websites.