Panverse, a new publisher of all-novella anthologies, is currently accepting submissions for Panverse Two, its second anthology, which is due to be published in late spring 2010.
They're looking for "pro-level" novellas of 15,000 to 40,000 words. Science fiction or fantasy - but not epic fantasy or sword & sorcery. Payment is $75 per novella. Submissions are open until they have enough good stories for the anthology.
Full guidelines are here. Note especially the sort of stuff they don't want.