I have used firefly and it works great, but I haven't tried it on my sheevaplug yet (since I don't use apple products and I haven't found another application for a daap server).
Try using aptitude, since there should be arm builds of most progs in the repos through apt-get. I think it's called mt-daapd.
apt-get install mt-daapd
apt-cache search mt-daapd
to find what the package is called if the first doesn't work. Let us know the results.