I am currently reading a pretty good collection of flash fiction. It's titled, Sudden Fiction: American Short-Short Stories, edited by Robert Shapard and James Thomas.
Not every collection of very short fiction has been particularly pleasing. I can't, for example, recommend Flash Fiction: 72 Very Short Stories, Edited by James Thomas and others.
But the differences between the two collections have more to do with taste than anything.
The first has some excellent writing, but more importantly has complete stories. The second is mainly 'stories' in vignette form. I'm not a fan of vignette, or slice-of-life as it is sometimes called. It's akin to peaking in a random window in a random city, seeing what's happening there but without knowing why it's happening or why I should care about what's happening. It's a device used often in literary fiction and narrative non-fiction but not one that appeals to me.
Some writers of such fiction claim it is supposed to engage the reader by leaving the unsaid up to the reader's imagination.
I don't know. To me, that's not why most people read. Which is why popular fiction is so, well, popular, and literary fiction is so, well, not.
But I won't harp on the poor writers of literary fiction.
I think you'd rather like to know where you can find some really great (or maybe not so great) very short fiction:
100 Malicious Little Mysteries, edited by Isaac Asimov
Flash Fiction Forward: 80 Very Short Stories, edited by Shapard and Thomas
Sudden Fiction (Continued): 60 New Short-Short Stories, same
Sudden Fiction International: 60 Short-Short Stories, same
New Sudden Fiction: Short-Short Stories From America and Beyond, same
Flash Fiction Online (of course!)
Vestal Review (stories of 500 words or less--mainly literary/mainstream)
EveryDayFiction (little bit of everything--a new story every day)
365 Tomorrows (daily sci-fi flash)
Cafe Irreal (very literary, but some interesting stuff there)
Glossolalia (VERY literary--often more poetry than coherent story in style;this'll give you an idea of what is meant by 'high literary.' Like it? Neither do I.)
Flash Me Magazine
Long Story Short
Podcasts and MP3 Downloads:
Sniplits (Some flash; MP3 Downloads)
Podcastle (Fantasy flash and short stories, podcast)
Pseudopod (Flash and short horror Pods)
The Drabblecast (flash and short stories of mixed speculative genres)
Happy reading (or listening)!