PBS
Pbs: The Native Americans
The Corps of Discovery came into contact with "Nearly 50 Native American tribes." This site from PBS discusses the tribes that had the most significant interactions with Lewis and Clark.
PBS
Pbs the West: Sacagawea
Part of a comprehensive site on the American West, this page explains Sacagawea's legendary role in the Lewis and Clark expedition.
PBS
Lewis and Clark: Inside the Corps: Sacagawea
An overview of the life of Sacagawea, the only woman to travel with Lewis and Clark on the great journey to the west.