Mostly instrumentals here, since those work best as background music IMO.
The Coldest of Wars - something like this for the first two 'spy' missions this one's for the last mission, obviously 
-- Z.
I've got to chime in on this, it's a great idea. As a lover of movie soundtracks, I'm kind of surprised/ashamed I didn't think of it myself in any concrete way. I'll need to contemplate what to use for my arc.
City of Heroes Musings (an official "fan site," now less maintained): http://dwarflog.blogspot.com/
"Project Dragon" would have the music from "International Karate Plus" or "Enter The Dragon". Personally I go to a youtube playlist with different versions of the IK+ soundtrack and listen to it while I play.
"Arena" was based on "Chess", and its soundtrack is the original cast concept album.
"Et In Arcadia Ego" is about my character "The Dreamlord" and his personal soundtrack has always been Coil's soundtrack for the Hellraiser movie, and that would suit the arc quite well I believe.
I'm not sure about the rest of my arcs.
Winner of Players' Choice Best Villainous Arc 2010: Fear and Loathing on Striga; ID #350522
I do dark/horror arcs so a few tracks that have inspired mine have been:
Twinkle- Les voies infectees
http://www.myspace.com/twinkleaudiot...ctees-25611914
Akira Yamaoka- Laura Plays The Piano (from Silent Hill)
http://www.youtube.com/watch?v=i6L9Cbs0m_U
Friends of Dean Martinez- Lost Horizon
http://www.youtube.com/watch?v=ikAggi6fZn4
Rapoon- Hollow Flight
http://www.youtube.com/watch?v=qTPDnj9WkVA
Pharos- Longitude
http://www.myspace.com/pharosambient...o-mix-27471051
Pharos- Desert Trance
http://www.myspace.com/pharosambient...rance-27471048
Behind The Veiled Mask
Arc# 526759
I had been meaning to post this for a while, but a recent thread reminded me of it. I know you can't have custom music for your arcs, but if you could, what would your arc's soundtracks be?