I am also a fan of the 'nonfiction' sources for Apocalyptica.
Definitely check out The World Without Us:
http://www.worldwithoutus.com/index2.html for how the planet, and particularly our urban-industrial centers would respond to suddenly not having us around to maintain them. It's a really fascinating book and a keystone for thinking about this stuff.
One of the things that makes it interesting is that he goes over several places in the world where 'mini-apocalypses' have already happened, forcing people to abandon population centers in a hurry. The aforementioned Appalachia gets some play, and you see a bit of it in the video posted earlier, but the craziest thing there is Centralia, Pennsylvania:
http://en.wikipedia.org/wiki/Centralia,_Pennsylvania, a town completely abandoned due to a mine fire that has been burning underneath since 1962(!!!).
They also talk about Cyprus, where the Civil War demilitarized zone necessitated abandoning a fully-functional modern resort community:
http://listverse.com/2008/03/10/top-10-interesting-abandoned-places/ (Actually, that last link has a wealth of amazing Apocalyptica... check out that mind-blowing abandoned 'pod village' in Taiwan, and of course, Chernobyl.
Someone mentioned comics, and there's a wealth of good stuff out right now: Wasteland, Y the Last Man, DMZ (particularly well-suited for the vibe of AW), Zero Killer, and classic stuff like Kamandi and Killraven if you want to go really gonzo.
For my money, the most interesting right now are 'Resurrection', an AW set after the invading aliens who destroyed civilization mysteriously up and left, and 'Irredeemable' and 'Incorruptible', which as superhero comics are light on the AW-type stuff, but present a pretty compelling vision of what a world where Superman decided to
just be a total dick would look like.
-Jim C.