io9: 18 Perfect Short Stories That Pack More Of A Punch Than Most Novels

"I'm a failed poet. Maybe every novelist wants to write poetry first, finds he can't, then tries the short story which is the most demanding form after poetry. And failing at that, only then does he take up novel writing." --William Faulkner

...and flash is best.

and the toughest--s6

I've just read Julie Phillips's biography of James Tiptree Jr and I've started Tiptree's best-of collection Her Smoke Will Rise Up Forever, both prompted by the fact that Tiptree's centenary is in August. The next one in the collection is one of the ones on the list at the start of this thread, "The Girl Who Was Plugged In" (really a novelette or short novella than a short story).

Plenty on that list I haven't read. Better get reading, then!