Plusfy is a web player that add new features to Spotify: mood analysis, favorite tracks, music importation into Spotify's library from audio files, disabling tracks, copy playlists and more.
Plusfy is under development ๐๐ทโโ๏ธ, but you can already test it here. (not anymore because of the end of the Heroku free plan)
Current only available in portuguese (Brazil). English available soon.