Well, to start with, a lot stuff from
Kahvi.org would work well, methinks. Apart from that, let see...
Aphex Twin - Xtal (If you have only heard come to daddy and are worried this is a joke, its not. This is back when he did ambient stuff)
Ilaria Graziano - Where does the Ocean go? (This is from the Ghost in the Shell: Stand Alone Complex OST 1)
Oh! Xerxes' album
The Mirror Formula! You can grab it
here, though I suppose you only want tracks, not a whole album... hmmm. I would think that track 5, angelina is probably best for sleeping. Boards of Canada probably have some good stuff for sleeping too, but I'm not so familar with their stuff to name songs of the top of my head.
Dangit. Thats all I got for now. Sorry I couldn't be more specific with the names. ^_^
EDIT (because I am a slow, slow poster): I would think that Explosions in the sky would be a little too excited to fall asleep too. But if thats what we are looking at in terms of energy, I'm going to add M83 - Lower Your Eyelids to Die With the Sun.