This comes from a Webjay competitor called Project Playlist. Looks to essentially search for hosted MP3s, then lets the user create a playlist out of them, and then embed the player into your site of choice.
Here's a random one:
The site is an absolute mess - there are ads everywhere and you search is less than useful. But...
UPDATE: I got rid of it, it didn't seem to have a way to turn Autoplay off and it was really starting to get annoying.