I was disappointed to discover that Pow Fast Flash Fiction has gone under. I just found out about this excellent, cross-genre site late last year when Sandra Seamans named a piece from there in her top five and now they're closing shop. Guess that's the way of the zines, they come and they go.
However, they will be keeping up their archives. A couple of stories I really dug there were Dog Fight by Aaron M. Wilson--an original, bizarre and brutal horror/spec fic piece--and Duke's Av's by Jim Bronyaur, which comes with the lesson that you should never underestimate the power of a pair of sunglasses.
Anyways, head over there and have a look around. If you like your fiction imaginative and bite-sized, Pow Fast is bound to have a piece you'll enjoy.