Below you can find a list of curators working on projects associated with music and the provision of freely licensed material, which could be used with the XOs.
Free Music Project
The Free Music Project, sponsored by the Free Culture society, is putting together a collection of iconic music from cultures and genres around the world. Their initial target is the OLPC audience of children and teachers; see freemusic.freeculture.org for details.
This group is working with Antenna Alliance and Jamendo to curate global collections for children.
TempoStand is a group testing out using CC-BY-SA music for all of their remixes and as backgrounds for other productions, out of India. All the music on their site is cc-by-sa: Tempostand.com