Suggestions that may be questionable in the eyes of some (purists?) would be Burl Ives who "popularized" quite a few overplayed well known folk songs, at least in the US.

Also a little off the mainstream, Marais & Miranda achieved a degree of popular recognition for some songs with a degree of "faux international" appeal in the late 50s(?).

I'm not sure either of these would be worth specific mention/discussion, but the songs they sang might be source material for figuring out what songs might have been at least transient fads the general population might recognize as "folk."

Most of Ives' repertoire pretty much mirrors what was in typical midwestern US grade school "music" books in the 40s-50s, while M & M were perhaps a little closer to what the brownies/girl scouts might have thought folkish 3 or 4 decades back. (The cub scouts I knew then didn't sing all that much. Burping rude words was about their limit.)

In the US, the idea of "folk" doesn't extend back much beyond the late 1700s for most people, even if some lore was "inherited" into the traditions from earlier origins elsewhere, so there likely would be some difference in approach for that audience than for others with longer roots. It may or may not be significant to recognize this difference(?), depending on how broad your audience is.

John