They don’t seem to be updating anymore, but BestScienceFictionStories is a really useful collection of info. It’s very searchable and well-tagged. Each entry tells you where the story can be found, either for free or for purchase. Someday, I want to have a classroom library of this stuff.
You can never have enough Bradbury. When I was teaching in Alaska, we used Holt’s “Elements of Literature” curriculum, which – at least at that time – featured some Bradbury stories, especially in its 2nd course (8th grade.) I think it’s great that Farenheit 451 has become a staple of secondary-school classrooms, but I think people forget that he was primarily a short fiction writer – an incredibly prolific short fiction writer. He left behind hundreds of short stories. In fact, many of the sci-fi grandmasters were really prolific in short fiction formats. Asimov, especially comes to mind; Anderson, Le Guin, Heinlein, Clark, Linebarger and others to a greater or lesser extent.
The Game of Rat and Dragon – Cordwainer Smith (A.K.A. Linebarger) A tragically underrated writer. Linebarger is the best of the best.
The Last Question – Asimov. I would love to teach this one sometime.
To be honest, this is the kind of thing that is dangerous for me. My love for certain things (like classic sci-fi, Hemingway, the romantic poets, Lewis, Beowulf, and Buffy the Vampire Slayer, to name a few) is really disproportionate. If I had my way, kids would come out of high school knowing more about Nicholas Van Rijn than algebra, the renaissance, or how to write a resume.