The MusicIP Playground
MusicIP now has a flash-based Music Discovery app called the 'playground'.
With the playground you can browse around their online music collection (about 30,000 tracks), listen to clips of songs, and most interestingly, get a set of 'similar sounding' tracks using the MusicIP song similarity engine. It's a pretty light-weight way to try out their similarity system. For the most part, the playground gives you an interesting similarity set, but does give a clunker every once in a while (does Led Zep's 'Immigrant Song' really sound like 'Just Don't tell Me That' by N'Sync?
Check it out, it is a pretty well-polished interface.