This is the link to Every Noise at Once, an interactive map of all genres of music.
Click on a genre to hear an example. Click the ">>" on any genre to see artists in that genre... and then click on any artist to hear an example of their work: Click "Scan" to let it play random samplings of everything on the page. I wonder how long it will take before this gets monetized by iTunes, Spotify, Pandora, Songza, etc.?
It worked for me in Chrome, but not in Firefox.