You will need:

• Raspberry Pi
  I used a Model B for the Ethernet port. You'll need to find how to add wifi yourself if you use a Model A
• USB Sound Card
  I used a Soundblaster Play USB as it was cheap at my local Canada Computers. (Sound quality isn't bad either)
• SD Card
  Minimum 2Gb. As long as you can install raspbian. After I was done, I only used 1.1Gb.

Step 1: Install Raspbian

Head over to www.raspbian.org and get your brand new Pi running with it. However you choose to install doesn't matter. Just get a basic system with network/ssh access going (don't install the "Debian Desktop Environment") and come back for step 2.

Step 2: Add software
For there to be music, we need some software to play it. As root run:

    apt-get install mpd cifs-utils alsa-base alsa-utils alsa-oss oss-compat alsa-plugins

This installs:

• CIFS Utilities. Useful for mounting SMB shares (coincidentally where my music is located)
• MPD. Music Player Daemon, the root of this project.
• ALSA. Useful if you want sound output.

Now that this is all installed, let's get some music playing!

Step 3: Configure MPD

Configuring MPD isn't too ridiculous. Just read the comments and google for the more challenging questions.

Fire up your editor of choice on /etc/mpd.conf.

Essential config items are:

    music_directory = <dir> # Set this to your library

    bind_to_address “any” # Useful if not a static IP

    # Following allow autodiscovery over zeroconf/avahi
    zeroconf_enabled “yes”
    zerconf_name “Boombox MPD”

    # Audio output for my sound card
    audio_output {
            type            "alsa"
            name            "My ALSA Device"
            options         "dev=dmixer"
            device          "plug:dmix"
    }

    mixer_type “software” # My soundcard mixer is in software

Step 4: Just add Music

Add the following to /etc/fstab to auto-mount a network share on boot:

    //X.Y.Z.W/Music /mnt/Music cifs credentials=/root/.credentials,iocharset=utf8,file_mode=0777,dir_mode=077 0 0

With /root/.credentials being a file that contains:

    username=<your username>
    password=<your password>

and X.Y.Z.W being the IP of your file server.

Run as root to mount your share:

    mount -a

Now you should have access to your music!