I have a cd book packed full of children's cd's on top of my fridge. At particular times of the day (usually after snack in the morning, and before or after dinner in the afternoon) we pop in a cd. We are HUGE fans of Raffi. I don't think any singer can soothe children quite like Raffi can. He's practically magic. We listen to the other children's cd's in this cd book as well, for variety. But there is one cd that is not designed for children, yet I would rank it almost as high as Raffi: The Beatles. Children love The Beatles. Check out our newest member of the Beatles Fan Club.
A lot of their songs are so simple, and easy for children to understand (at least on their level). We play the album "1", which has mostly upbeat songs. Thomas's favourite is "Yellow Submarine". I think there should be mandatory Beatles endorsement in any ECE program. I bet there are some really great health benefits for kids and daycare providers alike!