Happy Camper
Headphoneus Supremus
Check out Grace Potter (and the nocturnals).
Of course Christine McVie has an excellent voice. Check out the Fleetwood Mac songs that she sings and compare them to the Stevie Nicks ones - there is no comparison.
If you want to go Folk/Rock then Sandy Denny is hard to beat (early Fairport convention and then solo albums plus Fotheringay).
Most of this music is from another (ancient) age but what can I say, I'm old.
Enjoy the music - it's important.
I agree, Christie is better. http://www.youtube.com/watch?v=cdFqIDhGfzQ
Sandy Denny was such a talent. http://www.youtube.com/watch?v=n2xODjbfYw8&feature=fvwrel
Heyley Westenra
http://www.youtube.com/watch?v=G6SvkMr7LHM&playnext=1&list=PL8BB7B62D3C5A1B0F&feature=results_video
http://www.youtube.com/watch?v=2uZCYrPB2FM