The first side of This Mortal Coil's It'll End in Tears album sends me away into a perfect sleep. Sadly, the second half has the Power Pop of "Not Me" that could break the spell although it is a good song in itself.

If you wanna sleep, listen to Gilles Diederichs : Dodo dans tes bras (sleep in your arms)
Listen to it just ten seconds and you'll really feel slow down, like if the gravity begins to be more intense. You start yowning after one minute even if you're fully awake. :p

Radiohead. That stuff's relaxing as hell.
I can fall asleep to pretty much any type of music though.

I don't usually listen to music when I fall asleep, I prefer to read.

But when I do listen to music, it is usually Keith Jarrett's solo piano improvisations, like the hour long Bremen performance (obviously, I don't listen to the entire thing).

OR something like this.

I used to fall asleep listening to music up to a few years ago but it's something I've started doing again due to my insomnia creeping back. I find that listening to music while falling asleep helps me feel more relaxed and leads to a better nights sleep, instead of sleeping for only 3 hours or so.

As much as a cliche it might seem, it's usually ambient music or gentle acoustic music. The Tired Sounds of Stars of the Lid has been my album of choice lately. A couple of tracks each night is all I need to send me off to sleep (in the best way).

my go to sleep album:

http://www.metal-archives.com/images/2/9/6/4/29644.jpg

Die Festung by Paysage D'hiver

best paysage album too imo

Dead Can Dance: Aion

Normally I like silence for sleeping but I can deal with this

http://ecx.images-amazon.com/images/I/51CTE19X6RL.jpg

I used to listen to music every night whilst sleeping, but having a roomate has kind of stifled this. When he's not crashing here I like to put on music while I sleep, and I'll go right to sleep and stay as such until sunrise. Any music that I like will do, but I generally listen to drone music like Keiji Haino, Sunn O))), or La Monte Young when I sleep to music.