All the Disney stuff is great, but I would add to that the soundtracks from the animated movies always have fun songs that kids love. I used to listen Beauty and the Beast, Aladdin, Lion King and Pocahontas nonstop.
[ame=http://www.youtube.com/watch?v=OHR9uJLS3XA]YouTube - Pete Seeger - Abiyoyo[/ame]
[ame=http://www.amazon.com/Pete-Seegers-Greatest-Hits-Seeger/dp/B000063WD4/ref=sr_1_3?ie=UTF8&s=music&qid=1232557035&sr=1-3]Amazon.com: Pete Seeger's Greatest Hits: Pete Seeger: Music[/ame]
[ame=http://www.amazon.com/American-Favorite-Ballads-Vol-1/dp/B000067URK/ref=sr_1_5?ie=UTF8&s=music&qid=1232557035&sr=1-5]Amazon.com: American Favorite Ballads, Vol. 1: Pete Seeger: Music[/ame]