Libnds has finally been officially updated and its a doosy.
A lot of updates, changes, and features have been added to the mix. Top on the list are:
New Sound and Music library called maxmod (www.maxmod.org)
New background and sprite API for greatly simplified access to the 2D hardware.
dswifi, and maxmod are now included in the default arm7.
New FIFO system to support interprocessor comms.
Be sure and click update on your devkitPro installer and grab the latest tools.