I always need music to fall asleep to, so i have playlists, mix cds, etc. for things like this. Here are 5 of the songs I like.
Sigur Ros - Staralfur
Iron & Wine - The Trapeze Swinger
Jose Gonzalez - Heartbeats
Air - Alone in Kyoto
Cat Stevens - The Wind
All of these songs are very peaceful and pretty quiet but still beautiful songs. Now of course, this is just my taste in music, but these are great to fall asleep to.