According to Boutell.com
There is currently no well-known “youtube for MP3s.” Many have come and gone, probably because of the liability issues involved when people inevitably upload copyrighted music, especially with high quality settings.
A common and rather effective workaround is to create a simple movie with Windows Movie Maker or iMovie, using still photos (or just one still frame) for the video and your MP3 for the audio, then upload that to YouTube. Users respond well to this because they are familiar and comfortable with YouTube. The presence of even a minimal amount of visual content will help engage users who are used to having that component.