The Indian Law and Tribal Law & Government page posted by the University of Montana School of Law posts links to a wide range of legal materials relevant to American Indians. The collection includes treaties, laws, regulations, cases and links to other collections.
FindLaw provides well-annotated links to relevant government agencies.
The National Indian Law Library (NILL) posts a substantial collection of tribal constitutions, codes, treaties, court opinions and other primary and secondary legal materials.
Lexis offers a collection of Native American legal materials to be found by following the path "Search > Legal > Area of Law - By Topic > Native American Law." The collection includes treaties, tribal court opinions, Bureau of Indian Affairs, Presidential orders, Cohen's Handbook of Federal Indian Law, news and gambling-related materials.
Westlaw's Native American legal materials can be found by clicking on the "Directory" link at the top of the screen and then choosing "Topical Practice Areas > Native American Law."
VersusLaw offers a database of judicial opinions from tribal courts. (Note: Although VersusLaw is available only by subscription, you can get a 1-day subscription for a modest fee.)
Many of the leading U.S.-Indian treaties are reprinted in Documents of American Indian Diplomacy: Treaties, Agreements, and Conventions, 1775-1979.
The Encyclopedia of United States Indian Policy and Law discusses U.S. laws related to Native Americans (CQ Press).
The Rights of Indians and Tribes (Oxford University Press) is a popular and helpful 1-volume discussion of U.S. Federal Indian law.
The United States Tribal Courts Directory (W.S. Hein) contains contact information and a brief discussion of each court.