Marie Lu posted on her Tumblr her playlist of songs during the drafting and revising of Champion. I’ve gathered them up for you to listen to here.
She by Abney Park
We Are Pilots by Shiny Toy Guns
Soldiers by Drowning Pool
Mad World cover by Gary Jules
Those Without Fear by Audiomachine
Do You Hear the People Sing from Les Miserables
Illuminati by Audiomachine
I Can’t Make You Love Me cover by Bon Iver
Dragon Rider by Two Steps from Hell
Last Agni-Kai from Avatar: The Last Airbender
The Boy Who Trapped the Sun by Cooper Down
Imagine by John Lennon
I Will Always Love You by Whitney Houston
Promise by Thomas Bergerson
You can read about why she chose these songs here.