ywriter6, by SpaceJock. It's functional and it's free. It does not do as much as Scrivener does, but a few things it does somewhat better (imho). Not enough for me to switch, though.
Currently working on a handful of novel-length fiction projects. Most of them are swords & sorcery tales. When I find I'm blocked on one, I shift to another. A couple of them will likely never see publication (noob trash, which only certain authors can get away with publishing).