iHeartRadio is what I use and I've found a lot of good stuff.
You can get radio stations on it and build playlists based on bands or songs and new music will show up in those playlists similar (or it'll branch out, if you change your settings to do so) to what the playlist is set at.
It's an iPhone app, not sure if it's an app for anything else but they also have a website.
Anyway, it's pretty awesome. My dad is actually the one who told me about it at first and I've found a lot of cool stuff.
Plus if you listen to the radio stations, and you can select them locally or nationally, you can hear some pretty cool stuff also (well, depending on what you select).
Although, I've always found iHeartRadio's set-up on mobile to be a little confusing in some places but overall it's been pretty good to me. Downside is you can only skip songs you don't like a certain number of times a day. But if you set up multiple playlists, you can switch between them and the songs will change each time - so it's a good way to bypass the skipping limit.