Listen to this history of ballet from NPR's Fresh Air:
There's also a good history of ballet here on the Encyclopedia Britannica page.
Another great place to start is the Classics for kids show on ballet which focuses on Tchaikovsky.
This book has the stories of a lot of popular ballets and is a great introduction.
This nonfiction reader shows what it is like to be a ballerina working for a big company.
I couldn't decide which of these books I wanted to feature, so I decided to show both. The biography is wonderful, and Misty Copeland's own book Firebird is excellent
Music in our Homeschool has a neat 15 minute music lesson on Aaron Copeland with links to videos of some of his songs.
There's also a Classic for Kids podcast on Aaron Copeland's Cowboy ballets.
Particularly interested in the Nutcracker?
Try these Montessori themed Nutcracker printables.
Listen to the story of A Christmas Nutcracker from Story Nory (also available on itunes and Google Play Music).
Listen to the show on Classics for Kids on the Nutcracker.
This one isn't free, but Erica from Enrichment Studies has a beautiful collection of Fine art pages on ballet for $9.99. You can print these on cardstock and display them for years to come. (This is my affiliate link. Thanks)