I don't think we have a thread like this already, so I thought it might be neat to have a place for us to share markets we've submitted to where we've had good experiences. By which I don't necessarily mean just "they bought my story" but "the editor treated me professionally" or "I got very good feedback on a rejected story from this market" or "Damn you, JJA, for rejecting my story in under five minutes!"* etc.
* Which is good because, hey, JJA! And then you can send it elsewhere. 
With that in mind, I'd like to recommend Freeze Frame Fiction to those of you who write flash fiction. (In the interest of full disclosure, the editor is a writing friend from back in the day.)
In any case, I submitted there twice, got very thorough feedback the first time on what did and didn't work for the first readers (similar to ASIM) and garnered an acceptance the second time.
More importantly, the turn around time was very quick (roughly a week) on both submissions, and I've been paid already ($10) a few days after the acceptance--even though my story isn't scheduled to appear until July.
URL to guidelines are here: http://freezeframefiction.com/submissio ... lines-faq/
Stewart C Baker - 1st place, Q2 V32
My contest history: Semi-finalist, R, HM, R, R, HM, HM, R, R, R, R, HM, R, R, R, R, Winner
If only I could write flash... But I'm glad there's a market for you who can!
http://nineandsixtyways.com/
Tools, Not Rules.
Martin L. Shoemaker
3rd Place Q1 V31
"Today I Am Paul", WSFA Small Press Award 2015, Nebula nomination 2015
Today I Am Carey from Baen
The Last Dance (#1 science fiction eBook on Amazon, October 2019) and The Last Campaign from 47North
If only I could write flash... But I'm glad there's a market for you who can!
Write a regular length story and arbitrarily delete ten words out of every fifteen. That's how I do it! 
Stewart C Baker - 1st place, Q2 V32
My contest history: Semi-finalist, R, HM, R, R, HM, HM, R, R, R, R, HM, R, R, R, R, Winner
I might have to delete more than that! I'm starting to find a fairly consistent metric: if I list out the significant incidents in my story and count them, I'm pretty consistently finding I write 1,500 words per incident. So a flash story would be a fraction of one incident. I would have to learn to imply incidents so I don't have to include them AND use fewer words for the incidents I do include. It's a part of the craft that eludes me so far, so I applaud you for doing it so well.
http://nineandsixtyways.com/
Tools, Not Rules.
Martin L. Shoemaker
3rd Place Q1 V31
"Today I Am Paul", WSFA Small Press Award 2015, Nebula nomination 2015
Today I Am Carey from Baen
The Last Dance (#1 science fiction eBook on Amazon, October 2019) and The Last Campaign from 47North
I have a few flash in different genre including general fiction and romance. Oops, that one might be a bit over-I will have to double check.
Working on turning Lead into Gold.
Four HMs From WotF
The latest was Q1'12
HM-quarter 4 Volume 32
One HM for another contest
published in Strange New Worlds Ten.
Another HM http://onthepremises.com/minis/mini_18.html
