One of the most common questions is "What did American Indians eat?" Of course, the answer to this question varies from tribe to tribe. As you might be able to guess, Athabaskan Indians in Alaska had a very different diet from Brazilian tribes in the Amazon rainforest. Some Native American tribes were also much more agricultural, staying in one place year-round and farming the land, while other tribes were semi-nomadic, moving frequently from place to place as they hunted and gathered food for their families. This also affected what kinds of food they ate.
Here are some links to American Indian food sources and food gathering techniques the people developed over the years to fit these needs.
Native Languages.org: General Overview with some links
Tahtonka.com: General overview with specific foods and recipes
Wikipedia: General overview with specific foods and lots of recipes
American Indian Health and Diet Project: Very specific recipes focusing on the healthy aspects of the Native Diet
The Cooking Post: Native foods available for purchase