Neo-atheism is the acerbic, shrill polemics of writers like Richard Dawkins, Sam Harris or Christopher Hitchens who disparage and refute the truth of the Bible. Unlike their predecessors, they exhibit both a ferocity and antagonism to religion which borders on the manic and seeks to demonize the traditionalist and fundamentalist strains of Christianity and creationism. It also promulgates an excessive zeal for evolution or Darwinism. This is exemplifed by Dawkins being known as Darwin's rottweiller.
The contrast between "traditional" atheists and neo-atheists is that the former merely studied philosophy and rarely pushed their views on anyone, whereas the modern neo-atheists are essentially anti-religious activists.