Mt-Daapd is a daemon that shares MP3s from your linux box to iTunes clients.
Go to the above website and there is .deb .rpm etc etc. Works on a debian testing box here.
Setup is pretty straightforward, make sure the mt-daapd user (or whichever user the daemon runs as) has read access to the MP3s (this is important if you use an NTFS volume which mounts readable by only root in the first instance.
No page links to Mt-Daapd.
http://www.mt-daapd.org/