This is a new encyclopedia dedicated to music, much like IMDB is for movies. It’s still in beta, but is easy to use (it can auto-detect data from existing Amazon products) and has a design more like Virb and last.fm than Wikipedia. Like Wikipedia, you can add extra media like pics, audio and video (though they obviously feature more prominently here, since it’s music only) and external links relevant to the artist/release/label you’re editing. Unlike Wikipedia though, it’s subject to moderation before the changes show up on the page (takes from an hour to a couple of days).
This won’t be useful for everyone, since they only accept proper releases on the site (my album and NIN Remixes collection were accepted, but the loose bundle of ‘Non Album Tracks’ was rejected for not being a proper release, which is fair enough), but since this has Amazon and IMDB behind it, it certainly looks like it could become a useful resource to be a part of.