I also "discovered" a site this week that I've heard of for over a year now, called iLike. I've seen widgets from the site on the web before and no doubt have seen a few hundred thousand posts in Facebook from people who've installed their app. What I really like about iLike (that sounds corny to type, btw) is that it has a feature where I can import a playlist I made in iTunes into the site and it turns it into a postable widget (see below and the "Current Playlist" in my blog's sidebar).
Where iLike seriously lacks, and I dare say even loses all together, is that their workflow for managing playlists is terrible. As a UX practitioner myself, it's painfully obvious to me that many of the sites features are probably half-baked ideas some developer or product manager came up with that were thrown together in a hurry and later had features tacked on. For example, even finding a recently uploaded playlist from iTunes is nearly impossile. I actually caved and copied the unique ID number for the new playlist out of the address bar, opened an existing playlist for editing, and changed the ID number in the address bar to that of the new one. That it was that much easier for me to do it that was is simply shocking. If people aren't using that feature, I can only wonder why.
So that being said, here's my latest playlist, ready and set on the iPhone for my drive tomorrow. (I also completed my album of MGMT's Oracular Spectacular and threw some older but still good local music from Arizing on there too).