Sure, let's try this out! I've been denied from 365tomorrows a couple of times.
My favorite is http://www.gwthomas.org/flashshotindex.htm, and not merely because they've accepted me more than any other site. You read things there you are likely to never see anywhere else. Also get some of the most open-minded visitors to your own place of wiritng by referral.
"Another of your forum posts seemed to indicate an interest in horror and the like..."
Truth be told, I really like all of it; I am highly eclectic. I would like to see 6S be a veritable smorgasbord of all genres and forms: six sentence essays, political commentaries, reviews, sci-fi, spiritual, Christian, conservative, liberal, etc. I would love to see 6S become a huge melting pot! I am just tying to figure out if everything is welcome or if there is a particular emphasis?
It's less than a month active so I've only got one guest piece, and submission isn't currently open. But it will be soon, so if you write Speculative Flash fiction of Contemporary Fantasy pieces, hold on to them and get ready to send them in!
As for the rest of these sites, I'm upset now because I have way more reading ahead of me. Thanks guys.