Musicovery is a pretty interesting Web site. It’s basically a free music player, with limited selections. The trick is that you set the selections to meet your mood. You choose various genres, then choose your mood — from Energetic and Positive to Calm and Dark.
After all that (which takes maybe 15 seconds), you get a sort of mind-map schematic with a dozen or so songs listed, and one starts playing. You can click on any of the others and play them. It’s not a bad way to discover songs or artists you hadn’t known before.