Originally Posted by Chris Rezendes

I actually needed to listen to my mp3 players to fall asleep for a few years. Then my last zune died (it's what they're built to do) a couple of weeks ago...

I was actually close to building a slumber playlist right before it happened. I find certain albums to be unbelievably relaxing and help me drift off into sleep. Perhaps counter-intuitively, all of those albums are metal. A few off the top of my head-

Morbid Angel - Gateways to Annihilation
Sadus - Swallowed in Black
Pestilence - Malleus Maleficarum
Suffocation - Breeding the Spawn
Watchtower - Energetic Disassembly
Monstrosity - Imperial Doom
Destruction - Release from Agony
Megadeth - Peace Sells
Sepultura - Arise
Sacrifice - Forward to Termination
Morbid Saint - Spectrum of Death

I find that albums with a dark production work best, but those with an atmospheric production also work well, as do those with a lot of mid-paced songs.