XSPF

XSPF is a playlist in XML format. It is a free and open format so can be easily, freely used for sharing playlists.

What does XSPF look like?

A very simple document looks like this:

<?xml version="1.0" encoding="UTF-8"?>
 <playlist version="1" xmlns="http://xspf.org/ns/0/">
    <trackList>
        <track><location>file:///mp3s/song_1.mp3</location></track>
        <track><location>file:///mp3s/song_2.mp3</location></track>
        <track><location>file:///mp3s/song_3.mp3</location></track>
    </trackList>
 </playlist>

There are many advantages to using XML as the format. More information is available at Xiph.org's XSPF project website.