UPDATE: Apparently, a photographer deliberately misled AP reporters in the story I've striked out below. See here for more information.
A bit afield from the usual fare on this blog (though not wholly unrelated), I highly recommend this AP news article on Amazon tribes that have had little contact with the rest of the world.
The article also says, "Survival International estimates about 100 tribes worldwide have chosen to avoid contact, but said the only truly uncontacted tribe is the Sentinelese, who live on North Sentinel island off the coast of India and shoot arrows at anyone who comes near." The contents of this Wikipedia entry, however, would seem to conflict with the claim that the Sentinelese are "truly uncontacted." In any event, the Wikipedia entry also makes for interesting reading.