Listening your favourite songs that hosting at your Ubuntu server or desktop (or even on FreeNAS / NAS) on the road is your dream.
If you have a Nexus One or Android 1.5+ smartphone (or even iPhone), your dream comes true with Firefly (mt-daapd) and Ubuntu desktop/server.
It also can share your songs over your network with Rhythmbox or Banshee (or even iTune) on any desktop.
Please follows the instructions here to make this comes true.
Enjoy!