Wikimedia
Wikipedia: Indigenous Peoples of the Americas
Looks at migration theories proposed in regard to the early peopling of the Americas, European colonization, early agriculture and culture. Also looks at contemporary indigenous groups, then groups within each country in the Americas.
University of Calgary
Peopling North America: Theories Regarding First Migrations to the Americas
An overview of the multiple theories of the earliest migrations into North America.
BBC
Bbc: North America's First People
Easy-to-understand explanations for the theories revolving around first Americans. Each theory: Clovis First and Pacific Coast Route, is explained as well as the basis for the debate.