Yes, e-Reads has a very good selection of quality backlist sf/fantasy and mystery/crime. You'll be more easily able to see their offerings
at their website, and they've got buy-links to lead you to the listings at Fictionwise.
Depending on how old school you want your reading to be, they've got a lot of Harlan Ellison's classic short stories, Fritz Leiber, and they recently added some Robert Silverberg (with new introductions by the author himself), Pamela Sargent, and Elizabeth A. Lynn. I especially recommend out of the authors I've personally read: R.A. MacAvoy (fantasy, but very good, Campbell Award nominee, IIRC), Elizabeth Ann Scarborough (fantasy, but again very good, Nebula Award winner), George Alec Effinger (only read a few, but enjoyed very much; everyone says Budayeen series his best work), Aaron Elkins (mystery/crime thrillers, Edgar Award-winner, Gideon Oliver series has forensic science in it, highly recommended). I also quite enjoyed works by John DeChancie (comedic fantasy/sf), Ru Emerson (crossover RL/fantasy quest), Marta Randall (far future sf & mystery), Clare Bell (historical/anthropomorphic fantasy). I've also read good works out from other publishers by the following authors: Dave Duncan (fantasy & some sf), Greg Bear (sf), Alan Dean Foster (more sf), James R. Benn (historical mystery/crime thrillers).
Other publishers with reasonably high quality sf/fantasy in their catalogues whom I'm going to assume haven't removed their books from FW to only sell elsewhere yet are Wildside Press (erratic about updating their FW offerings; especially recommend Brian Stableford's Biotech Revolution stories; his old school space operas and "gothic decadence" stories not nearly as good, IMHO), Prime Books (only a small selection because likewise erratic, but good quality modern authors), Quintamid LLC & ElectricStory.com & Wonder Audiobooks (good source for collections of single-author shorts; WAB has old-school stuff, some of which is collected US public domain, but others of which are still in copyright by older living authors, so check before buying). Mid-quality newbie sf/fantasy publishers which have a couple of good backlist authors in their stable are Mundania Press (Don Callander, Anne Logston, Louise Cooper, etc.), Mushroom Press (had 2 people who were previously published by DAW, can't remember their names), Double Dragon Publishing (Kenneth C. Flint, Nick Pollotta).