Mediatomb is an free open source UPnP server for Linux and Mac OS X. It allows you to stream media (videos and music) to networked devices for playback, and has an (admittedly grim) web-based GUI.

Installing in Ubuntu or Debian is easy (for other distros please check the website). First, add the gpg key so the package can be verified:

   wget http://apt.mediatomb.cc/key.asc -O- -q | sudo apt-key add -

Add the following line to /etc/apt/sources.list:

   deb http://apt.mediatomb.cc/ feisty main 

(Note that although the package specifies "feisty" it will work in the new "gutsy" i.e. Ubuntu 7.10.)

Now install like normal:

   sudo aptitude install mediatomb

Unfortunately the version here doesn't seem to support MySQL as a backend.

Of course, you will want to add your music too. If my music collection is at /opt/share/Music:

   sudo mediatomb --add /opt/share/Music

Now you can tune in with a music player such as Rhythmbox or iTunes