From Planet Fox:
General MIDI's Jukebox is a lightweight jukebox style MIDI player. It comes with a slick user interface designed to look like a hardware MIDI synthesizer from 1989 and the ability to load, save, and edit playlists.
It uses the software MIDI renderer built in to Java to play MIDIs with more realistic sounding instruments and better sound quality than the software MIDI synthesizer included with Windows Media Player.
It's super portable at only 72kB in size and doesn't need to be installed. Just click on the .jar file and you're up and running. Perfect for background music, DJs, and karaoke. Requires Java, which can be downloaded for free at the Java website.