To the names that Deb Cowan mentioned, let me add the following in no particular order:

Pat Humphries
Sandy Opatow
Holly Near
Alix Dobkin
Ruth Pelham
Bev Grant
Jamie Anderson
Charlie King
Karen Brandow
Luci Murphy
Joel Landy
Judy Gorman
Fred Stanton
Eliot Kenin
Si Kahn
Kim Harris
Reggie Harris
Larry Otway
Bob Blue
Paul Kaplan
Jon Fromer
Len Chandler
Patricia Shih
Collen Kattau
Utah Phillips
Rosalie Sorrels
Matt Jones
Sharon Abreu
Tom Neilson
Phil Hoose

and of course...

Pete Seeger
Peggy Seeger

I am certain other Mudcatters can add to the list!