Bert Jansch was one of them-- probably the one you heard least about. I've posted about him before, and Dr. K has linked to some of his work with Pentangle. Anyway, on the event of his death, a proper acknowledgement is in order.
As a folk guitar player, he reminded me more of Nick Drake than probably anyone else has. He didn't have Drake's beautiful voice, and he strayed from genre more often, which probably limited his appeal. (At least with this generation; I know he was fairly big in the '60s.) I'm no folk music expert, but I think he remained pretty widely revered in today's folk community, both in England and the U.S.
As recordings go, "The Best of Bert Jansch" is a pretty good retrospective, although he put out a whole bunch of albums. And I myself need to hear more Pentangle, especially after reading the NPR obituary linked to above.
I was more of a casual fan than any sort of expert on his work. All I can say is he was a special musician, and he died much too young.