I ran across a submission call for flash ebooks that's going to put out by Pagan Writers Press. There will be three flash collections: Paranormal Romance, Erotica, and Halloween/Samhain. Their flash length is 1000 to 2500 words. The deadline for this call is March 1, payment is a royalty split. You can find the call here.
Submissions are through Submittable and checking there I found that they're also looking for novella length work of 15,000 to 35,000 words for their Twisted Tales line, novels in a variety of genres that includes Mystery/Suspense, and non-fiction books about the art and business of writing. You can find all these guidelines here as their website doesn't have much information.