Databionic MusicMiner
Continuing the theme of visualizing large music collections ...
The Databionic MusicMiner is an open-source music browser that uses data mining techniques to create 'MusicMaps' that visualize the similarity of songs and artists. The maps allow you to explore your music collection and create playlists directly from these maps.
Here's the browser interfacce:
Here's a MusicMap:
This system was developed by the Databionics Research Group at the University of Marburg, Germany. This group has released a number of open source tools that perform data mining tasks such as clustering, visualization and classification with Emergent Self-Organizing Maps. There's a paper giving an overview of their toolkit here: ESOM-Maps: Tools for clustering, visualization, and classification with Emergent SOM