My favourite lullaby, "The Swan" from Camille Saint-Saens's "The Carnival of the Animals". I used to listen to this as I fell asleep. Between the melody itself and the cello playing it, by far one of my favourite pieces of music.
You can't go wrong with The Andrews Sisters, either, despite the huge shoulder pads. Direct from the era of live radio productions, "Straighten Up and Fly Right". I use that line on my kids sometimes.
And last but definitely not least, the Buena Vista Social Club. Enjoy!