I have an idea for a post-apocalyptic campaign - not a hard crash but a gradual collapse of civilization. Instead of a Road Warrior or Fallout barren wasteland, imagine endless shanty towns, sprawl, refugee camps and shadow cities for most of humanity and fortified green zones for the privileged elite. Makers and fabricators spewing out pirated video games and AK-47s. Rumors of unnatural things in hot zones - the areas humans can't survive because of rampant pollution and toxic waste which was released by freakish weather or terrorist attacks. Sightings of an Armageddon Beast - an unstoppable killing machine that wanders the world, destroying everything it can. Husks - animate clothing that stalks the fringes and said to worship an impossibly tall man in a suit. There are zombies out there, but they're the least of your problems.
This is just such a colorful setting and I think it would be a lot of fun to play around in/listen to others interact with...
Some (but not all) influences
Cold war architecture as described by Fallout, the book Survival City and so forth. Bunkers, silos, esoteric industrial complexes built for no discernible reason.
Urban exploration and other oddities from BLDG Blog and the like. Architectural horror. The madness of banality.
Cities Under Siege/Shock Doctrine/McMafia/Global Guerrillas - the face of global instability today - sprawling, chaotic cities and refugee camps spiraling out of control, profit focused terrorists and franchise crime syndicates contrasted with the faceless institutions of corporations and governments that deploy widespread surveillance, co-opt civil rights and subvert any type of democratic reform
Junji Ito/Hastur/Carcosa/House of Leaves/House on the Borderland - cosmic horror with an emphasis on the unreal - did something actually happen or are you just going mad? Artistic decadence.
Some good inspiration could also be had from S.T.A.L.K.E.R. : Shadow of Chernobyl.
The game is set in Chernobyl in the near-future, where a second nuclear incident has occurred. Suddenly mutated animals start appearing and the zone is closed off entirely. However, there is also the discovery of certain irradiated artifacts with properties that defy scientific logic, which become extremely valuable. So, mercenaries start entering the zone illegally in search of fame and fortune, only meet the real horrors of the zone. They are called stalkers, and they are some of the toughest people around.
It has a lot of exploration, factions vying for power, mutants with crazy psychic powers, awesome gameplay and a kick-ass story. The developers are Ukrainian, and so they could easily travel to the real Chernobyl and render it faithfully in the game, so it's really immersive. There's also a ton of mods which add more content and better graphics to the game.
Definitely worth checking out, if you're gonna do the post-apocalyptic campaign.
