If you liked Audioscrobbler Browser, have a look at the demo videos and paper describing Elias Pampalk's MusicSun project. It's along the same lines, ie you add artists to the collection and it refines the list of suggested artists based on those, but calculates 'similarity' based on three features: audio (from Fourier analysis), word (from words on web pages containing the artist's name) and web (from similarity of web pages containing the artist's name). It has a nice interface, and also plays 20-second snippets from each artist, selected from each track using a chorus-detection algorithm.
Elias works at last.fm now, like just about everyone who completed a PhD thesis in music analysis in the last few years.