Ask HN: Recommendation services?

Can anyone suggest recommendation services?

What I'd like is a service to which I can send a simple query like "I like Jack Johnson" and it will tell me "You should also listen to Madeleine Peyroux, Indigo Girls and John Coltrane."

Or whatever, in some machine-queryable form.

I'm not interested in code. Or building up the corpus of data. I'm interesting in someone (Amazon? Pandora? Last.FM?) that already has a large, rich database from which it can generate results.