Normal things, like novels, short story collections, and so on are sourced from personal connections and not open for submissions. This will probably not change, as I have no shortage of work.
However, if you have something really awesome that is so far out of traditional categories you can’t imagine anyone publishing it, I’d like to hear about it. Things slanted towards science fiction, history of science, and other nerdy pursuits are the most likely to spur my interest. Short queries to email@example.com.