I've just come back, after having grabbed a bunch of works by the authors mentioned in Appendix N, as well as a few other works of interest.
For my collection of Appendix N authors, I managed to pick up:
Fantasy, by Poul Anderson
Image of the Beast by Philip José Farmer
The Dragon in the Sword by Michael Moorcock
Spell of the Witch World by Andre Norton
Swords Against Darkness IV, edited by Andrew J. Offutt
John the Balladeer by Manly Wade Wellman
Roadmarks by Roger Zelazny
Although I didn't grab them (having already purchased copies), deCamp's Lest Darkness Fall and Zelazny's Jack of Shadows were both there in the fantasy and science fiction section. The first was marked at $2, and the second was a hardcover but probably not more than $5. If you live in the Toronto area, and you are interested in grabbing these books, I wish you the best of luck. I am not sure how long they will be there.
Not Appendix N, but interesting/useful, I picked up:
Life in the Medieval University by R. S. Rait
The Medieval Castle by M. E. Reeves
Medieval Women by Eileen Power
Njal's Saga, Penguin Classics edition
Hecate's Cauldron, edited by Susan M. Schwartz
The Stone Book by Alan Garner
Overall, I spend under $40 Canadian to obtain all of these titles, and I am pretty happy with my purchases. If you happen to live in Toronto, again, it is well worth your time to check it out.