Yesterday, BookFinder.com issued its annual report on books that are "out-of-print and in demand," i.e.

Book Dealer: Antiquarian & Rare
(425) 271-6481
Rare, collectible, used, and select books on the American & Canadian West, plus (more)
Book Dealer: Antiquarian & Rare
(845) 264-7256
Via Biblio.com: mathematics & science; history of science; first-edition fiction (more)