The first time I read about Carvaka, also known as Lokayata, was in a comment by Radical Hypocrite on one of the posts of his now unavailable blog. The Carvaka school of thought (its origins can be traced back to 6th century BC) is a materialistic and atheistic (Atheism in Hinduism) one that dismisses all ideas of God and afterlife. It seems to be the first philosophy to emerge out of India that actively preaches that happiness is the goal of one’s life. Not only that, it considers perception to be the only true source of knowledge (Carvaka – First chapter of Sarva-Darsana-Samgraha) –
The proper aim of a Charvakan or Charvaka, according to these sources, was to live a prosperous, happy, and productive life in this world.
– Wikipedia entry for Carvaka
Unfortunately none of the original texts related to this philosophy seem to have survived and Sarva-Darsana-Samgraha (available via the Internet Archive), a book written in the 14th century by Madhavacharya, one of the sankaracharyas of the Sringeri Math seems to be a major source of information. It seems Amartya Sen’s The Argumentative Indian (haven’t read it) has mentioned the philosophy as an example of the Indian atheistic tradition (his interview to California Magazine).