I think Loreena McKennitt's a cappella version of "She Moved Through the Faire," just for variety's sake...it is haunting as all get out (she does it with harp in concert for some reason)...

my additions to your wonderful compilation:
"Hammer Horror" by Kate Bush
"Raven in the Storm" by John Gorka
"The Witch's Promise" by Jethro Tull
"Season of the Witch" by Donovan
"I But a Little Girl" by Bob Franke
"You Will Burn" by Steeleye Span
"Twa Corbies" by Maddy Prior
"The Fabled Hare" by Maddy Prior