Atheists with brains might want to check out David Hume. He was an atheist with an actual capacity for argument, as well as a wonderfully fluent literary style. For intelligent anti-theist philosophy, see Dialogues Concerning Natural Religion. That ought to do you well, but if you want to get into ethical naturalism and other philosophical aspects of materialism, go ahead with An Enquiry Concerning The Principles Of Morals and An Enquiry Concerning Human Understanding.
I am sure acosmists feel left out. Please have fun with Spinoza, guys.