Technical news site TechCrunch has recently posted about JamJunky, a social songwriting site. JamJunky enables you to upload your songs so that other people can comment on them and help you improve the songs. Apparently, you can limit who can access the songs, so that you can only let your friends comment on them, or you can let anyone comment on them. CenterNetworks has also recently reviewed JamJunky and has provided a video review of the site.
JamJunky is an interesting concept, and it will be interesting to see if the idea catches on. Collaborative songwriting could be fun, if the implementation is right.