There is a sense in which Feuerbach utterly rejects religion and a sense in which his atheism is very religious. The reason for this apparent paradox is Feuerbach's view of what religion is. According to him, human beings in their attempts to deal with the world objectify their own being -- are alienated from it -- and then takes this objectified being as an absolute subject of which he is an object. In other words, in our attempts to understand ourselves and the world, we develop a sort of self-consciousness; this self-consciousness splits (so to speak) when we take features of our nature and treat them (due to sentiments of longing, wish-fulfillment, and imagination) as an individual person or being or force standing over against us, to which we are somehow subject. We start by taking it as our object, and then begin to think of ourselves as its object. Man's God is Man(Homo homini deus). As he states it in Part I, Chapter II:
Religion is the disuniting of man from himself; he sets God before him as the antithesis of himself God is not what man is – man is not what God is. God is the infinite, man the finite being; God is perfect, man imperfect; God eternal, man temporal; God almighty, man weak; God holy, man sinful. God and man are extremes: God is the absolutely positive, the sum of all realities; man the absolutely negative, comprehending all negations.
But in religion man contemplates his own latent nature. Hence it must be shown that this antithesis, this differencing of God and man, with which religion begins, is a differencing of man with his own nature.
This dialectic plays an important role in our coming to know ourselves -- finite minds come to understand themselves by externalizing themselves (in unlimited form) in the idea of God (or whatever is taken as equivalent to it); the last stage of self-knowledge is to recognize that the idea of God is simply a stage in the finite mind's understanding of itself. Religion is an aspect of our drive to live and know, and plays a key role in our growth into moral self-understanding.
Taken this way, we can see why Feuerbach is in one sense a sharp critique of religion and in another sense is highly religious. On this view, religionists are in a state of utter confusion; they are caught in the grip of wish-fulfillment and rational self-contradictions. However, on this view it is also true that the problem with religionists is not that they are religious, but that they become religious and stop, rather than continuing on to greater self-knowledge. Thus one way to put the view is this: there is a true essence of religion (an anthropological one, in which religious claims are understood as part of the finite mind's self-understanding) and there is a false essence of religion (a theological one, in which religious claims are taken in such a way that the human beings are objectifying their own humanity and not recognizing that they are doing so). The anthropological aspect of religion is a fundamentally important aspect of our moral life; the theological aspect is something that needs to be overcome, because theology is philosophical anthropology misunderstood. Because of this twist, Feuerbach was often criticized by other atheists as simply replacing one mysterious abstraction (the divine) with another (the human) -- the worship of abstract man, as Marx calls it somewhere. In other words, we have an abstract Rational Being doing most of what 'God' does in religious discourse, but called 'Man' rather than 'God'. Because of this Feuerbach in later works attempts to root the formulation of his position in the more concrete and sensuous life of actual human individuals, and to look more closely at confusion of names and things in theological discourse.
It was his earlier work, however, that primarily influenced nineteenth-century atheism (although the later work is perhaps more important for Marx and Engels, who are heavily influenced by Feuerbach), and it is this type of atheism that is typically considered to be Feuerbachian: Religion taken as the religionist takes it is a confusion and error, but it serves an existential function that nothing else does. The religionist is on to something; he has discovered genuine truth. His error lies in his interpretation of this genuine truth, which Feuerbach thinks is obviously confused, self-contradictory, and naively wish-fulfilling. Nonetheless, there is an atheistic interpretation under which the genuine truth of religion shows through. The only complete atheist is the religious atheist: and the reason the religious atheist is complete is that he has transcended the bounds of religionism. He is an atheist not by subtracting God from his worldview; he is an atheist by transcending God in his self-understanding. He takes the rich treasure of self-understanding lying hidden in religious life and transfigures it into an atheistic and naturalistic worldview in order to deepen his life as a human being. Atheism is not a more bare and limited position than theism; it is a richer and less limited position. Indeed, in a sense, the atheist is more religious than any religionist, because he has taken what was good in the religionist's position, but has cast away all the limits of it. Religion must be taken out of the field of faith and put into the field of reason. Such is (more or less, allowing for variation among different Feuerbachians) the Feuerbachian attitude to religion and atheism.
The most famous Feuerbachian is perhaps George Eliot, who translated The Essence of Christianity into English. Like all Feuerbachians, she's very eclectic, so it would be a mistake to treat her Feuerbachian side too narrowly, without taking into account the influences of Lewes, Comte, and the like. But she is very definitely Feuerbachian (as she says in one place, "With the ideas of Feuerbach I everywhere agree") it is in part because of her Feuerbachian approach to religion that we get some of Eliot's richness: she can be sharply critical of religious attitudes, but can also be very sympathetic towards them (as she is to Savonarola in Romola). The reason is that from her perspective religion is an error: but it is an error worth learning from. Eliot has a Comtean view that the human race has passed through three stages: theological (explaining the world mythically), metaphysical (the theological is refined and corrected), and positivist (we finally break through from abstract and obscure forces). Like any positivist (in the broad sense -- in her, Feuerbach modifes and broadens the narrow Comtean conception), Eliot thinks the positive attitude (again, in a very broad sense) is the right one; however, some of her works (Romola, again, is the most obvious example) criticize the view that you can simply be positivist by repudiating the theological perspective (like popular Christianity) and the metaphysical perspective (like more abstract philosophical deisms). That way lies disaster and self-deception. It's not quite the suggestion that you can't be an adequate positivist without having gone through these two stages yourself; rather, it's more of an implication that adequate positivism requires these two stages to have been gone through, generally, and that the positivist transcends rather than simply denies the theological and metaphysical. And this is where Eliot diverges from Comtean positivism in a Feuerbachian direction. For Eliot there is an essential connection between religion and morality; for her, as for Feuerbach, the problem with the religionist is that he stops with his religious views rather than seeing them as what they are, a form of moral thought that has been objectified as external to us. However, precisely because of this, Eliot makes considerable use of religious ideas -- many religious ideas are exactly right, as far as they go, but not under the interpretation the typical religionist wants to impose. And, what is more, those who cut themselves off from this source of moral thought stunt themselves: simply subtracting God rather than transcending God, they fail to come to an adequate self-knowledge. They are trying to reach the end of the dialectic of self-understanding without learning the truths that can be gathered from the self-objectification religion brings.
This characterization of the role played by Feuerbachian ideas in Eliot's work is a bit crude and simplified, and no doubt The Little Professor and other scholars of the Victorian novel could point out refinements that might be needed. But I think Eliot provides a good example of the sort of thing you can get in Feuerbach-style atheisms -- there are many variations, of course, since almost everyone diverges from Feuerbach in precise details -- which I think tend to be the most interesting sorts of atheism. It's relevant to the posts linked to at the beginning, in the sense that much of the discussion, especially in the comments boxes, tended to assume that no atheist would find religion to be anything but error, and that no atheist would hold that there is an essential and unbreakable link between religion and morality. But this is certainly false of almost any Feuerbachian atheist. It goes to show you how complicated this topic can get, and how diverse atheists are, when even atheists underestimate the diversity of atheists.
You can read selections from Feuerbach's works at the Feuerbach Internet Archive.