Last.fm is connecting people through music, and not just showering people with music. It's sort of a new kind of online radio. A radio that connects you straight with the right music without having to do mind-numbing searches and scrolling endless playlists.
A note: LastFM shares accounts with AudioScrobbler so if you're already using the AudioScrobbler's plugin to upload the info about your favourite music you don't have to register on Last.fm.