Goodreads hasn't been anyone's favorite place lately, but I do love what it has recommended for me based on my "Romance" shelf. Goodreads seems to know that my true love is space. Naturally when I'm in the mood for romance, I'd pick up a Scalzi book (I'm not even being completely sarcastic right now). I'm happy with whatever algorithm led GR there.
P.S. - I'd be really impressed if there was a dinosaur book recommendation in there too, since dinosaurs are my other love.