I've just submitted to Niteblade, so I thought I'd report on their submission system.
They take all lengths from drabble up to 7500 words, and pay a flat fee of $10 per story, plus pdf copy.
They use the submishmash system, so if you don't already have an account there you'll have to make one.
They require that the work is single spaced, with a blank line between paragraphs, and NO indents.
The indents is very important. They have an interview at Duotrope and they say there that if it is indented they will reject unread.
So. NO INDENTS.
They don't mention anything else, but when you get to the submishmash form it asks for either doc or rtf.
I got an automated acknowledgement almost immediately.
Hope this is helpful to someone, and good luck if you submit to them.