The world of end-of-the-world-or-maybe-just-civilization is vast and all-encompassing (that was my freshman composition introductory sentence. You're welcome). There's apocalyptic, post-apocalyptic, near-apocalyptic, dystopian, post-apocalyptic dystopian, zombie apocalypse, post-zombie apocalypse, and there's probably more I'm not thinking of. So in the interest of clarity, I'm going to define them, or at least give you my particular definition of them.
In terms of this blog, apocalyptic fiction deals with the apocalyptic event itself, and ends either with the aftermath (usually scenes of cleaning up and putting everything back together) or with the successful prevention of said-apocalyptic event. Most disaster movies go under this heading. Less concerned with the consequences themselves, they focus on the apocalyptic scenario. Case in point: 2012. Near-apocalyptic is related; in this sub-genre, the event is prevented from happening (think: Armageddon). I consider zombie apocalypse a sub-genre as well, since in these stories the zombie outbreak begins within the book and then must be dealt with by the main characters, like in Cell by Stephen King, for example.
Post-apocalyptic differs from apocalyptic because, in most cases, the apocalyptic event occurs before the beginning of the story, or at the beginning. The majority of the story concerns the events that happen after the apocalypse. Sub-genres of this would be post-apocalyptic dystopian (where the apocalyptic event most commonly occurs many years before the events of the story) and post-zombie apocalypse (where a zombie apocalypse occurred beforehand: think Zombieland).
Dystopian does not necessarily require an apocalyptic event, but it can in some cases (as in The Handmaid's Tale); dystopian stories feature societies that have become repressive and controlling, usually by means of a totalitarian or authoritarian government, which may or may not be religious in nature. Classic example: V for Vendetta.
As far as apocalyptic/post-apocalyptic (and most of its sub-genres) are concerned, there are several different flavors that it can come in: nuclear war, pandemic, failure of modern technology, extraterrestrial threats, the "cosy catastrophe"/natural disaster, and post-peak oil.
As you can see, the genre is pretty large. There are probably even sub-genres in zombie fiction, but I don't know them. There's no end to the end of the world!