i actually just made a list of my favorites right before i saw this! out of them, i'd recommend airbuds, cara, and last.fm the most!
airbuds is an app/site where you can see what music your friends are listening to and you can make a cool profile of music recommendations
cara is an app/site for artists with a great algorithm and i would use it more if i had more art to post and if people i knew were more active on it
last.fm is a music analytics website (they have an app but its not as good as the website) that goes pretty in depth about the music you listen to and recommends you some music too!