I first learned of the news concerning the "uncontacted" tribe in the Amazonian Rainforest from Wired. Some of the articles and news releases are somewhat misleading, making it seem as if this was the very first time that anyone has ever seen this tribe. According to a Wikipedia article, it should be termed as "isolated", with which I agree. These photos, however, are a very important reminder that there are others on our Earth that are more primitive in every aspect of their lives, and that have no need or desire to be included. There is much controversy as to whether or not civilized society should intervene in their affairs.
Perhaps the peoples with the least contact are the Sentinelese islanders of the Indian ocean.
Survival International is an organization devoted to protecting tribal peoples' rights. Their website is worth some attention.