Sockos is a personal music server that running on multi-platform. She is written in Java.
I integrated the music server in my home-made NAS and the how-to is here :
http://samiux.wordpress.com/2008/10/01/howto-home-made-nas-server-with-ubuntu-8041-%E2%80%93-part-vii/
Warning - If you want to share your music to others over the internet, you should beware the copyright of music industry or you may be in trouble - lawsuit.
You have been warned.
Enjoy your music at anytime and anywhere!!!!