What is morality without any god? This is a question that perplexes theists, but atheists (used in this post to cover atheists, agnostics, ignostics, and other non-theists) seem to have it all figured out, but do we? I don't think we do, really. Rather, when it comes to morality, we can be just as sectarian as religious people. Broadly speaking, there are two camps: the moral naturalists, such as Dan Fincke or Matt Dillahunty of the Atheist Experience or Sam Harris exemplified in the Moral Landscape, and the moral skeptics, such as Simon Blackburn or Russell Blackford or J.L. Mackie. Broadly speaking, moral naturalists posit some sort of really existing morality that can be discovered through some sort of naturalistic exploration, such as science while moral skeptics question the fundamental assumptions of morality, including if it is real, if it can be true or false, and/or if it can be discovered. The first two necessitate the third, though the third doesn't necessitate either of the others, and all oppose moral naturalism. The big name proponents of the two thus are from different sorts. The moral naturalists have a tendency toward being scientists, Dan Fincke being the one philosopher of my examples, while the moral skeptics have a tendency toward being philosophers. This is not a hard and fast rule, but a tendency I've noticed. Indeed, among atheists, those who are of a scientific bent and came to atheism from science seem to be largely moral naturalists while those who are of a philosophical bent and came to atheism from philosophy seem to be largely moral skeptics. There are certainly other views within atheism, but those are the two major camps. A good place to see this conflict is this recent reddit post. In it, a theist asks atheists where they get their ethics, and there is a roughly equal divide between people giving moral naturalist responses, such as "There are facts about what is and is not good for the health, happiness, and satisfaction of people. Being aware of these facts allows you to act morally." and people giving moral skeptical responses, such as "There is no absolute morality." Though, I should note, most seemed mostly ignorant of metaethics, while giving metaethical answers that fall within preexisting metaethical camps.
In addition, there is plenty of disagreement from within the camps. For example, Sam Harris derived his ethics from neuroscience while Dan Fincke derived his from categorical norms, such as, say, "truth" or science. However, by far, I find the divisions within the moral skeptical camp to be more interesting. Indeed, while there are differences within moral naturalism, they mostly amount to methodology, aka *how* do we naturalistically derive morals? However, the differences within moral skepticism gets down into deep metaethics. For example, Simon Blackburn is a quasi-realist, aka he believes that moral statements project emotional feelings as if they were real properties, thus, though they can't be true or false, they can be treated as true or false. In contrast, Russell Blackford is an error theorist, aka he believes moral statements *can* be true or false, but all are false. These are far more interesting to consider than whether we should discover true morals through neuroscience or through norms accepted a priori.
As for myself, I fall deep within the moral skeptics camp, aligning myself with the moral nihilistic emotivists within the camp, aka I believe morality doesn't truly exist because all moral statements are an expression of emotion, thus making "good" equivalent to "stuff I like" and, thus, meaningless as a separate concept.