Appendix N, the listing of fiction titles that Gary Gygax found inspirational for his own campaigns and spelled out in the AD&D Dungeon Master's Guide. Gary had said that he hadn't read Smith until after D&D was released, which seems strange as much of the feel of those early games closely resembles imagery found in Smith's prose.
It's a shame, then, about the lack of Smith's work in print. The Night Shade collections of his fantasy stories are going out-of-print, leaving only a mass-market paperback collection of stories as the most widely available text.
That will change March 25th, when a new collection of Smith's prose and poetry is published as part of the prestigious Penguin Classics series, edited and with an introduction and notes by S.T. Joshi.
My knowledge of Smith's writing is deficient, as I've only read a handful of stories. This new collection is terrific not only for me to read more of his work but as an acknowledgement of Smith's talent and place among the great world writers.
The final table of contents was posted to the message board at the Smith scholarship site The Eldritch Dark.