Musicovery dubs themselves an “interactive webRadio.” It’s basically a visual representation of musical genres that you can click around and explore. They provide a palette of moods to get you started, Dark to Positive, Calm to Energetic. Start clicking around and let the music wash over you. No registration required, they make their money from a subscription to their “hi-fi” version as well as affiliate links to purchase tracks on Amazon or iTunes.
UPDATE : Frederic Vavrille from Musicovery writes in the comments that the site Battelle was pointing to now lives at liveplasma.com. It appears that both Musicovery and Liveplasma are related. While Musicovery lets you click and listen while you explore, Liveplasma does not let you listen to music but adds Movies Titles, Directors, and Actors as vectors to explore.