I ran across Monster Corral over at ralan.com This is a flash market looking for stories up to 1000 words in the genres of sci-fi, horror, and crime noir. Their theme for 2013 submissions is the "extreme antagonist", or simply put, monsters of all types. Payment is 1cent a word. You can find all the details here.
UPDATE: November 22, 2013 Ralan.com has declared this a dead market.