I recently switched to SoundCloud free and the ads are really not that bad (only con for example if your playing off your phone and it hits a video ad you can't lock your device till the SD finishes). However if the device screen is locked you'll only get audio ads (short and sweet at that).

Like YouTube though it will suffer from take down notices on some stuff you book mark, as well as mainstream stuff you can only listen to the first 30 seconds (but I've never been big into what's radio popular).