Here is a list of (living)singers of traditional Child Ballads from my own collection of recordings. There will be some repeats of people already mentioned.

Peggy Seeger, of Asheville, NC
*Gordon Bok, Ann Mayo Muir, & Ed Trickett
Betty Smith
Jean Ritchie, of eastern Kentucky
*Tamara Sheen of eastern PA
Custer LaRue
*Mike Seeger, of Lexington, VA
Jody Stecher
Gillian Welch & David Rawlings (a very nice version of "Wind & Rain")
*Sheila Kay Adams, of western NC
*Ellen Gozion, of western PA
Debra Cowan
Acie Cargill, of Kentucky
*Bobby McMillon, of western NC
Phyllis Boyens
*Dwight Diller, of West Virginia
Diane Jones
Bob Heyer
Laura Boosinger (another nice version of "Wind & Rain")
John Roberts & Tony Barrand
Susan Brown
*Tracy Schwarz & Ginny Hawker, of WVA
*Doc Watson, of western NC
*Mary Jane Queen, of western NC
Norman Kennedy
*Ed Miller, of Texas
*Elizabeth LaPrelle, of VA
Cindy Kallet
Phyllis Marks, of WVA
        
I don't know if the following people ever sing Child ballads anymore or not:

Bob Dylan
Hedy West
Joan Baez
Judy Collins
Billy Edd Wheeler
Odetta

I also have tapes made by Gerry Milnes at Elkins, WVA of singers from WVA, but I don't know how many of them are still living: Holly Hundley, Everett White, and Clyde Case.      

*People that I have heard in person. T.O.M..