My story Blue and Yellow's soundtrack would probably be Just A Little by The Used... Only because one line in the chorus, and the overall feel of it, really inspired me when writing. I still put it on repeat sometimes when I'm working on new chapters.
For Insanity I listen to whichever song the chapter is titled after, so for the first chapter, I listened to Sick Hearts. After that I just have iTunes on shuffle on my playlist of The Used songs.
For 1888 I have a playlist of songs that remind me of Jack the Ripper and/or horror movies, murder, etc. This playlist's really varied compared to some of my other ones. I have songs from bands as widely varied as Marilyn Manson to Evanescence and Tarja Turunen. I have covers of Morrisey's song Jack The Ripper, as I don't have the original.
For my other stories, such as Click Click, I just put my iTunes on shuffle.
I wrote chaper two of Angelfuck mostly listening to Wolftron, who is this amazing asian guy named Kenny Choi who makes the most beautiful music I have ever heard in my life. I also threw in a little Lupe Fiasco and Mad World on repeat.
I made a playlist of quiet songs, specifically for when I'm writing... ...It has mellow tunes on it, like Interlude and Desert Song, Tool, A Perfect Circle and the Lord of the Rings theme tune.
I cannot work with heavy music, but, at the same time, I can't work in silence either :)
The unposted story (which I'm getting addicted to by now) called, "The World Is Ugly" was inspired by MCR's The World Is Ugly and Iron Maiden's Hallowed and Flight Of Icarus.