Last.fm also uses Spotify Premium streaming for its content, i.e. personalised radio stations based on your listening history or on-demand playback of any Last.fm page with tracklists like your personal charts or artist charts and albums. You can also listen to similar artists radios of classical music artists or tag/genre-based radio stations like "classical" etc. See the official announcement of the Spotify Beta Player for more info:
If you don't have a Premium account, you can also choose YouTube as your playback source in your Last.fm website settings.