Metal types or bands that don't yell

Clean vocals rule, but my favorite power metal vocalists are the ones with the raspy afertaste, like Urban Breed from Tad Morose.
 
Solitude Aeturnus
Sieges Even
Psychotic Waltz
Shadow Gallery

Some female-fronted bands:
Nightwish
Dreams Of Sanity
The Gathering (try "Mandylion" and "Nighttime Birds"; their newer albums aren´t metal anymore, though this doesn´t necessarily mean you won´t like them)
Nemesea (you can download one full-length song from their record label´s website)
Soulslide (you can download one full-length song from their website)