I'm currently halfway through S. M. Sterling's Dies the Fire, where all of a sudden all modern technology stops working at once, to include the fact that suddenly gunpowder no longer burns. After all planes fall out of the sky at once, humanity comes to the sudden realization that we're pretty much screwed, and all of a sudden those guys from the Society for Creative Anachronism have a leg up on the type of survival skills it's going to take to keep alive once the easily-available canned food runs out....
Johnathan