My former colleagues at OFAI have been experimenting with audio content based music recommendation for FM4 Soundpark for a while now. (I blogged about it here.) Now they (and in particular Martin Gasser) have taken it a few steps further and implemented a 3D exploration interface using the islands of music metaphor.
It's all in Java and requires special privileges because it needs access to low level graphics card functions. But if you get passed those hurdles here's what you'd see:
(Navigation: space bar, A,W,S,D and mouse)
There is more information about this and other recommendation tools they have developed for Soundpark here (in German).