UPDATE for 2020 – An excellent in-depth look at the situation by Andrew Grant: How Much Does Spotify Pay Artists & Has It Killed The Industry?
Great graphic here from Information is Beautiful: Major Music Streaming Services Compared
Daniel Sanchez breaks down some of the info from that graphic: What Streaming Music Services Pay
And this one is outdated (most of the services are paying LESS just 2 years later) but still a helpful graphic: How Much Do Artists Make Online
And this more personal account from Isaac Shepard: My Music Royalty Rates Over The Last Two Years