Seems to me that the Spotify API opens up all sorts of possibilities for music discovery.
Sharemyplaylist.com is basically what makes Spotify useful for me at all. I still can't talk to anyone, but at least I can have a playlist that sounds roughly like the songs belong together. I'll rarely discover new music on it.
For music discovery, I find http://hypem.com and mp3 blogs to be far more useful. Still no strong community, but at least I actually discover new interesting things.