TuneGlue, another musical preferences mapping service, hit the news last week. TuneGlue draws on data from last.fm and amazon.com. I saw it mentioned on The Music Weblog and Hypebot. I can't really see much difference between that and LivePlasma, which in addition to mapping out "music that sounds like <your preference>" also maps out movies and directors that draw on similar viewer preferences.
I think LivePlasma takes the trophy home though... when I search Sigur Rós on LivePlasma, it points out a newish compilation CD from Iceland that looks interesting. That might make a nice Xmas stocking stuffer for someone.