Rhapsody has always allowed you to email a playlist to your friends. In the bad, old days of the original interface, this meant you got an attachment of a .RPL file. I never really opened one up to figure out how it worked, but it seemed to work okay.
In the new interface, I only get a URL that points to a playlist identified by an ID number. No playlist name, or user ID, or encryption string. Just a number. So, I quickly wondered whether I could look at other playlists using the same method. And I can.
BTW, the link is in the sidebar of this website. Enjoy.