Outside of the classical realm, I find myself mostly drawn to "world music" flavors and especially to songs not in English so that the language itself forms part of the musical-artistic effect. The particular qualities of vocal timbre are quite important, too. Lately, what has the strongest hold on my musical sensibility are sensuous Latin forms, especially those involving the gorgeous sound of Brazilian Portuguese, which I'm beginning to learn.
There are three women I am intensely passionate about.
One is Zulya Kamalova (http://zulya.com/ -- you can hear samples of most of her stuff on http://cdbaby.com/, alas not on Pandora at all yet)--especially when she sings in her native Tatar. She is a master of many languages and has a really startling and unique mix of instrumental sounds, and a truly original compositional style.
Another is the multi-talented Brazilian, Mônica Salmaso (http://www.monicasalmaso.mus.br/). When I came upon her version of "Canto em qualquer canto" on youtube (with no video in it -- there's another youtube one with a video of her group playing this but with very inferior sound), I just about <i>died</i> of astonishment at its power and beauty and its transcendence of merely pleasant traditional idioms while still having a gorgeous surface all the way through. And that feeling did not diminish at all over my next ten hearings. Lately I've been trying out many other Brazilians, but she remains at the very top.
Finally is another Brazilian, Paula Morelenbaum, whose voice is very special in a different way: extremely pure and clear. A few youtube videos capture her quite wonderfully.