So I'm being curious and spotted this website about writing post-apocalyptic novels. It includes six resources for various apocalyptic events, including the good ole favourite, zombie invasion. It includes asteroids, bombs and atomic explosions, along with maps and scientific answers in reference to the devastation. It's pretty cool - I found out what a WWI bomb would do to my town - and is just fun to play around with, even if it's just as inspiration.
Happy apocalyptic writing! :D