This plugin makes it simple to add custom music playlists including:
Preview from iTunes
Album or Collection
Links to iTunes
Unlimited Musicboxes and tracks. Drag and drop re-ordering of tracks and Musicboxes. You can set the widget to play automatically or require the user to press play first. The widget will play through all of the tracks.
The plugin's functionality does what it says. To fully make use of it, you'll need to be able to handle some CSS.
Aside from that, the Developer conveniently inserts their own iTunes Affiliate ID to all Links created by the plugin.
It's easy enough to change, but you just have to be aware and search; it's not mentioned in any documentation...
That sneaky trick would normally bring the rating waaaay down, but since I found it easily enough and can change it and the functionality is what I need, so yeah.