TrueMusic is a pure-Java music player supporting mp3, Ogg Vorbis, Ogg FLAC, Native FLAC, Speex, WAV, AU, AIFF, SND and MIDI.  It is free software under the GNU General Public License.  It utilizes jFLAC, JavaLayer, J-Ogg, Java ID3 Tag Library and JSpeex.  Requires Java 6 or later (Vista users already have it).