Thanks to a wonderful new similarity algorithm from Amnon Amir and a heap of new Creative Commons-licensed data from the Audioscrobbler server, the Audioscrobbler Browser has been hugely improved.
It's a dynamic TouchGraph visualisation, which shows links between similar artists, calculated by analysing shared listening trends (more details of the algorithm used can be found on the Audioscrobbler wiki). Double-click on nodes to expand the graph, and play with the settings to adjust the level of detail - hopefully you'll find some new bands to seek out.