I ran across Wolf on Water Publishing over at Duotrope. They're looking for novellas of 10,000 to 15,000 words in the genres of sci-fi, horror, experimental, and anything punk. They also have a horror anthology call with the title "Specter, Shade, Visitor, Blade". You can find the submission details for both here.
There is no mention of payment for either call so that is something you should query before proceeding. There is also no mention of who is in charge of this enterprise but there are a few books already published (could be the owners). My biggest concern here is that they title themselves as Wolf on Water Publishing Services so before you agree to anything be sure that you're not footing the bill. I hate having to add cautions but it's better to be safe than sorry.