Check out the Intergalactic Medicine Show:
We are looking for stories of any length in the genres of science fiction and fantasy.
"Science fiction" includes hard sf, sf adventure, alternate history, near-future, far-future, psi, alien, and any other kind of sf you can think of.
"Fantasy" includes heroic fantasy (based on any culture's mythology), fairy tales, contemporary fantasy, and "horror" in the sense of supernatural suspense (not gory bloodfests, thanks).
Within these genres, we like to see well-developed milieus and believable, engaging characters. We also look for clear, unaffected writing. Asimov, Niven, Tolkien, Yolen, and Hobb are more likely to be our literary exemplars than James Joyce.
We pay 6 cents a word.
Although they specific 'any length', I suspect in practical terms you wouldn't want to go much longer than 10K words. Turnaround is about 3 months.
Note also that their electronic submission form will send you the details on how to make your submission, not actually accept your submission directly.
Submission guidelines here: http://www.intergalacticmedicineshow.com/cgi-bin/mag.cgi?do=content&article=submissions