Wikipedia has a list of
apocalyptic & post-apoc fiction. Also, the
page about the genre includes some lists, with notes about common themes and so on.
Post-apocalypse is my favorite genre (Theme? Topic?) and I tend to include books in it that don't show up on the normal lists. Atlas Shrugged. (I have a special fondness for social apocalypse, where it's not a war or a plague but gradual breakdown of society until too many little processes have stopped working, and large systems start to collapse.) Starhawk's
The Fifth Sacred Thing. Boyett's
Ariel. Butler's Xenogenesis trilogy.