As the other tributes on this site make clear, many fantasy readers feel that Lin Carter's death was both an individual tragedy and a loss to the republic of letters. His contributions to fantasy can be gauged by the amount he published and edited, but what readers really lost is harder to measure.
While I enjoy much of his fiction, especially his short pieces, it is as an editor and scholar that I first encountered him and I miss him today. He represented an approach to literature (and not just fantasy literature) that's becoming rare nowadays. Carter was first an amateur, in the original and best sense, of books and reading, and second a writer and editor. He had the faults of an amateur -- he sometimes paraded his learning -- but his true magnaminity always shone through. In his gusto and enthusiam for the books he edited, he simply couldn't help but mention a half dozen obscure gems he thought every lover of belles lettres ought to know. Those who followed up on these tips thank him for his large hearted erudition.
I, for one, owe him a debt of gratitude for making bibliography, footnotes, and all the panoply of scholarship interesting to a 13 year old underachiever in small town Texas -- an achievement he couldn't have anticipated in his most fantastic fiction.
As a young reader of fantasy, I eagerly devoured anything by or about my favorite authors. Carter's "Tolkien; a Look Behind the Lord of the Rings", replete with scholarly apparatus, was a bibliographic gold mine. I spent years scouring book stores and libraries for works Carter discussed in this book. His chatty, informal learning also influenced me in another way: though nearly two generations separated us, he represented a model of a "man of letters" to which I could aspire. Neither he or I were nourished exclusively on the classics -- he grew up with pulp and radio, I with TV -- but he combined his popular and cultivated interests in a way that helped me to see there was something to this business of "real" literature after all. Though he had a special love for fantasy, Carter also communicated a zest for literature in general -- in contrast to some of today's leading fantasy editors, whose stodgy enthusiasms seem to be limited to making weird fiction respectable in academic circles.
Unfortunately, my grades didn't improve till I got to college, when my early enthusiasm for bibliography came in handy. However, while I can't credit Lin Carter with turning me into a scholar, he certainly opened doors for me no teacher ever did. For that I'd like to say: Thanks, Lin Carter.