A few of the songs that I sleep to:
"Copacabana" by Barry Manilow
Various numbers from musicals, usually Les Mis, Lion King, Wicked, Phantom of the Opera, etc.
"A Moment of Silence" and "Somewhere in the Between" by Streetlight Manifesto
Anything by Reel Big Fish (i really dunno why. most of their stuff isn't very mellow. I think it's just the familiarity)
A lot of Green Day's slower songs.
Various brony songs. ie "Right Here With Me" by Mysteriousbronie, "I Am No Hero" and "Long Way From Equestria" by MandoPony, several of Odyssey's stuff, mostly "Luna."
I have odd musical tastes