I only know of "Only Time" which is pretty bloody famous here. Yet if you played it to the public, everyone can hum along but there's like a 5% chance anyone would know who sang it or what was the name.
Amarantine was also a quite pleasant album which I downloaded but just couldn't listen in full and gave up after a week.
That thing she does to the vocals is amazing. I love the layering. Reminds me of some Tori Amos stuff.