CloudTunes: your web-based music player for the cloud

Great idea and execution from Jakub Roztočil:

CloudTunes provides a unified interface for music stored in the cloud (YouTube, Dropbox, etc.) and integrates with Last.fm, Facebook, and Musicbrainz for metadata, discovery, and social experience. It is similar to services like Spotify, except instead of local tracks and the fixed Spotify catalog, CloudTunes uses your files stored in Dropbox and music videos on YouTube.