I'd known of these ancient Indian atheists from Jennifer Michael Hecht's Doubt: A History. I don't remember reading this much about them before. They seem to have been near clones of Epicureanism, or modern humanism. 300 years ealier (600 BC), no atomism, also no silly autistically happy gods like Epicurus had, more explicit feminism than I've seen in surviving Epicurean writings (though Epicureans are said to have welcomed women).
http://en.wikipedia.org/wiki/Carvaka
http://www.humanistictexts.org/carvaka.htm
http://www.swaveda.com/elibrary.php?id=17&action=show&type=book
UPDATE: Indian atomism. I don't know if it's linked to the Carvaka but it's mildly interesting anyway.
http://en.wikipedia.org/wiki/Atomism#Indian_atomism
http://en.wikipedia.org/wiki/Carvaka
http://www.humanistictexts.org/carvaka.htm
http://www.swaveda.com/elibrary.php?id=17&action=show&type=book
UPDATE: Indian atomism. I don't know if it's linked to the Carvaka but it's mildly interesting anyway.
http://en.wikipedia.org/wiki/Atomism#Indian_atomism