A few to start with:
Andrews, Edward        Gift to Be Simple
Beldin, H.M.        Ballads and Songs Collected by the Missouri
Bush, Michael         Folk Songs of Central West Virginia, v 1-4
Carawan, G & C        Voices From the Mountains
Cazden, N&H Hau        Songs of the Catskills
Combs, Josiah        Folk-Songs From the Kentucky Highlands
Davis, Arthur K        Traditional Ballads of Virginia
Doerflinger, W        Songs of the Sailor and Lumberman
Eckstrom, Fanny        Minstrelsy of Maine
Eddy, Mary O.        Ballads and Songs From Ohio
Johnson, J W        American Negro Spirituals
Linscott,Eloise        Folk Songs of Old New England
McNeil, W.K.        Southern Folk Ballads, Vol 1-2         
Owens, William         Texas Folk Songs
Randolph, Vance        Ozark Folksongs (abridged)
Richardson,EthelAmerican Mountain Songs
Ritchie, Jean        Folk Songs of the Southern Appalachians
Shoemaker, HenryMountain Minstrelsy of Pennsylvania
Warner, Anne        Traditional American Folk Songs